Apple's watchOS is likely to see some slowdown in the early part of 2016 as anticipation builds for the second generation device. However, with newer hardware and an evolving ecosystem, Apple will remain the smartwatch leader through the majority of the forecast.
Android Wear remains in second place as its list of partners grows and the platform further integrates into Google's larger ecosystem. Google's decision to limit UI differentiation will stifle further growth (unlike its success in smartphones) but this may have the positive side effect of forcing brands to compete on design and price, appealing to the fashion conscious, the budget conscious, or both. Adding Android-based smartwatches to Android Wear would push the category into first place in 2020. However, Android smartwatches are expected to remain a small portion of the overall market and will likely be relegated to emerging regions as local vendors attempt to differentiate themselves.
Real-Time Operating System (RTOS) – primarily used as a proprietary operating system but capable of running third-party apps – will become the third largest smartwatch OS, largely driven by gains in emerging markets and its use by Chinese ODMs. Appealing to consumers looking for a cheap alternative, RTOS devices will likely see relatively high adoption though the experience will be sub-par.
Tizen's limited app ecosystem makes it a tough sell as a smartwatch, though this underdog has the potential to pose a serious threat to Android Wear if Samsung is able to provide some synergy between its lineup of Gear S watches and the rest of its consumer electronics portfolio.
Linux-based smartwatches will have similar appeal as RTOS-based devices. The focus will be low cost and adoption will be mainly in the Asia/Pacific region, excluding Japan.
Pebble's avid fan base and unique hardware/software platform will enjoy modest growth in the short term. However, competitive pressures will cause it to gradually lose share to giants like watchOS and Android Wear.
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