Microsoft lost the OS war and is defending Office as best they can, which includes cross-platform tooling.
Already Google Apps has made a strong play, and Microsoft is doing quite a good job defending. Teams is only a part of it.
And there’s also mobile, which they lost entirely. That could be a risk, too, and they know it.
Businesses they still have a stranglehold, but even there I've noticed it loosening.
Guess we're in a revival of the 70s/80s mainframes with dumb terminals again.
Is that also your overall estimate on how long the mobile paradigm will overtake the desktop one? I would guesstimate that to a decade, or a decade and a half at most, with the degeneration of written language following closely.