It will be a long time before Microsoft Exchange, Active Directory, and Excel are not important enough to enterprises to justify the Microsoft subscription. And Visual Studio is still a huge part of the Microsoft capture strategy.
Microsoft is working on separating all of the above from Windows without losing too much control but it is going to take a while.
> Microsoft Exchange, Active Directory, and Excel
Exchange should be SaaS for 99% of businesses. There's a web version of Excel that's probably OK-ish. I'm not sure what Active Directory looks like in a world without Windows.