Microsoft will maintain their UWP strategy because they want to soft exit the console business. The end of the 360 era already saw them pretty reneging on building an exclusive library, and the XB1 now has a pretty dire selection of first and second party content. With development cost as high as they are, it makes no sense to invest in new first party studios or exclusive second/third party AAA content. This new strategy always them to heavily monetise a small base of console die-hards, mostly on third party content, while generating significantly less per user revenue on the massively popular PC platform. Since they don't have to build actual consoles/platforms, but just maintain the current one, their upfront investment is slashed. Build a cheap pc, name it Xbox and ship it is a lot cheaper than the XB1 and 360 design process.
At some point of microsoft store penetration, PC/XB exclusive content becomes cost effective again, so they can maintain their business at much lower costs then before, reflecting a lower risk. If the store is not a success (recent numbers, e.g. RottR indicate this), their lower investment allows them to fully exit the market at low cost.
