The pair will form the front line of Samsung's wearable army until the release of its next watch, and also hints that the Korean giant is still interested in keeping the S line alive and ready for a new instalment in 2018.
Essential reading: Inside Samsung's Design Lab
So users now have plenty of options to choose from, with two sporty designs packed with features and a more classic smartwatch watch which still offers that coveted rotating bezel. Not to mention the Gear Fit2 Pro, for those who want more of a fitness band styling.
But just how will Samsung top things next time around? Well, the Gear S4 is likely some way off yet, but we've explored what it could look like and what features users may potentially have on their wrist.
Gear S4: Design
Time to lose some weight
With the Gear S3 duo still considered by Samsung to be the leader of its smartwatch army, this is likely still the reference point to judge the next design from and not the sleeker Gear Sport.
With some sensors taken out of the latter in order to get to the final design, we wouldn't be surprised if the Gear S4 sat somewhere in the middle - all the same functionality under the hood of the Gear S3 but with the slimmer design of the Sport.
Earlier this year, Samsung announced mass production of its Exynos 7 Dual 7270 chipset, which is likely to power its next generation of wearables. It packs a lot of guts, including a 4G LTE modem (which didn't feature in the Sport), into a smaller package than is currently on offer. We expect it to feature on this year's device.
Samsung Gear Edge
So we've seen Samsung phones with curved screens, but will the S4 be next in line to get the edge treatment? A patent filed suggests that could well be the case, showing off a thin strip of a display formed on the edge of the dial. It would offer users a shortcut to apps with basic information like the date, time and weather available, too. The display would also only be rotated 90 degrees and is split into an upper and lower section, although it's not clear why.
You should always take patents with a pinch of salt, largely because many ideas end up getting dumped, but Samsung has showcased this kind of design before and is clearly a fan of the idea.
Another idea Samsung is keen on is flexible devices, and another patent, revealed back in 2016, outlines a wraparound wearable that's all screen. Samsung has already announced that it plans to launch flexible smartphones, and so a smartwatch version of this design isn't ludicrous to imagine.
Could we see it on the S4? Probably not quite as you see it above, but there may well be some flexible element in there if Samsung is as enthusiastic about this tech as it seems to be.
Bringing the juice
As we've noted above, slimming down is something that's fairly likely from the next line of Gear watches. But with companies consistently looking to pack more and more sensors under the hood, losing mass isn't exactly an easy thing to achieve.
That's why Samsung could move towards placing the battery for its watches in the strap, leaving it with plenty of options from a design perspective. While freeing up the space typically taken by a battery could signal a move towards more external sensors, it could also be used to reduce the size of the bezel dramatically.
Essential reading: Samsung Gear Sport v Gear S3
And let's not rule out the possibility that these extra batteries in the straps could simply be used to help push life past the typical couple of days, with no dramatic changes coming to the current internals.
Is it something that's likely for the Gear S4? It's hard to say. While Samsung has been at the forefront of developing flexible technology, seeing it drop later this year would still be a surprise.
Sub-display for rotating bezel
Similar to one of the patents above, which also shows off a second display, Samsung could be looking to bring more functionality to its rotating bezel through a future Gear watch. However, instead of a sub-display that appears on the outer edge of the bezel, this filing shows off a plan to upgrade the outer ring of the watch face.
According to the patent, users would navigate the Tizen OS by twisting the bezel to a specific segment on the ring, with each section dedicated to a certain app or feature. For example, between 4 o'clock and 6 o'clock you may have a segment which shoots you straight into your music when you rotate, and twisting further could send you into your unread notifications.
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Since introducing this wouldn't bring a drastic change to how the watch currently functions, it wouldn't be a surprise to see Samsung pack some kind of sub-display into the Gear S4.
Charging through the phone
As we all know, most traditional smartwatches haven't yet cracked short battery life issues, leaving you prone to a blank screen if you forget to charge for a day or two. But, as a recent Samsung patent indicates, the Gear S4 could make use of a smartphone in order to spring back to life and take on some juice.
Essentially, the device could be charged by a smartphone case simply by resting on top. The case would use a USB-C port to take power from a phone that, in turn, would provide power to the smartwatch using a hidden coil, just by touching it to a conductive plate on the case.
Of course, any patent faces an uphill battle to make it to a finished product, but this would be a nifty addition to help your wrist remain in the loop.
Samsung Gear S4: Features
We've explored the subject of blood pressure tracking in great depth, with the area presenting a big opportunity for wearable tech companies to make more elaborate methods a thing of the past, and now we know it's something that sits on Samsung's radar.
According to a recent patent filed by the company, it's created a method that uses light technology to take a blood pressure measurement. The device in the patent refers to a Samsung Gear X, which looks similar to the Korean company's older smartwatches, though there's a strong chance this is a placeholder design.
The big challenge for Samsung, as with any wearable company exploring the technology, is receiving FDA approval. If it's able to do so, it wouldn't be a surprise to see the feature pop up through the Gear S4, though this does feel like something that's still a couple of generations away from mass market devices.
Wherefore art thou Bixby?
Samsung's Bixby digital voice assistant launched alongside the previous generation of Samsung smartphones last year, and with its omission from the Gear Sport we expect it to eventually replace S Voice on the Gear S4.
After all, when we asked a Samsung rep if Bixby was coming to the Gear smartwatches in the future, he said: "Definitely, Bixby is the assistant that we're going to empower many other Samsung devices with – the watch, the TV, the fridge."
The rep noted that there's no specific roadmap for when the fully-fledged Bixby will arrive on wrists, but given that the smart assistant sat out of this year's smartwatch, it would be a major shock if it didn't make it onto the next flagship.
Where does S Patch fit in?
Since it first teased the idea of the dedicated health and wellbeing device back in January 2016 at CES, we've been waiting to see what would become of the S Patch. And while things stayed silent for some time, a FCC listing for the device recently surfaced, indicating Sammy is gearing up to launch an S-Patch 3 to the masses.
Just when that might happen is obviously unknown. But when it does eventually drop, it could feature some interesting interactivity with the company's next smartwatch, since Bluetooth connectivity is on board for the ride. This could potentially deliver data – such as PPG, skin temperature, galvanic skin response and body fat analysis – in real-time to the Gear S4, which could be fed into the wider Samsung Health picture.
Going big on health?
Samsung already bet the farm on sport and fitness with the Gear Sport, but it's likely this emphasis continues into its next smartwatch.
In an interview with CNBC earlier this year, Samsung Mobile chief DJ Koh said: "If we can put in place properly a smartwatch that can monitor everything for your health and provide the information, then the market will grow."
That sounds like a fairly solid ethos in place for the company, and would also fit in with the rebranding of Samsung Health and potentially even the launch of the S Patch discussed above. We expect the Gear S4 to tap into health in a major way, hopefully with some new sensors à la Fitbit, too.
Samsung Gear S4: Release date
With Samsung's last two smartwatches, an announcement has come at the end of August before a launch in November.
It's almost certain we see the Gear S4 unveiled at IFA 2018 in late August/early September, with this generation's Gear Sport representing a stop-gap before the Gear S3 is replaced as the flagship smartwatch.
With Apple, Fitbit and more competitors consistently releasing their rival options in the run-up to Christmas, it would be a shock to see Samsung deviate from its now-routine launch cycle.
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