The whole ecosystem is changing, and so maybe we dont demand so much from the OSes in themselves anymore, at least not in terms of feature-set itself.

Enterprises are not equipped to cope withe Steve Jobs style new OS every year - they want standardization and stability, and often be able to deploy their own build which they don't have to change for years.

Every time a new significant OS or SP comes out, many enterprises feel the need to do security audits, complete compatibility checks, acceptance testing while running their enterprise apps, rounds of 'training' for the people who can't work out how to do stuff on their own, etc.

Lots of reasons behind that, many will end over time. But for now that is why you don't see a lot of new feature orientated updates from Microsoft.