Linux

The desktop has been losing market for a while. I feel Windows is already under serious threat (if not already in the minority) when you think about all the devices that mainstream audiences orbit around (phones, tablets, portable consoles, etc), often using the Linux kernel. Only about a third of most website traffic comes from desktops.

Many of the people who frequently use Windows desktop do so because of their job, and often avoid using it outside of work as much as possible, since it feels like.. well, work.

Microsoft has been desperately trying to appeal to those other bigger sectors of the pie and has failed every time.

PC Gaming was one sector they had advantage on, yet that has already started to crumble thanks to Valve. I feel that MS will just try to push for integrating their xbox with Windows OS more and more...

I feel it's a battle with many fronts, since PCs have many uses.. so MS is likely to run their typical spiel: copy what the competition are doing and try to centralize/integrate it with their OS in a way that gives them an advantage, as they are famous for doing.

Another sector they can do this is with the WSL (Windows Subsystem for Linux)... they could turn Windows into a frontend for running Linux apps... so if Linux apps became popular, they could try to advertise Windows as the "best" way to run Linux software without losing the full first party support of legacy Windows software.