If only Microsoft released Office for Linux and Apple let OSX run (in a VM or otherwise) on non-Apple hardware the world would be a much better place.
If Apple let OS X run on other hardware the OS would suffer with them having to spend time supporting so many different configurations. If they didn't their reputation would suffer. Microsoft building Office for Linux would be a complete waste of time and money. The majority of Linux users would complain that it was expensive, closed source, and continue using the free, open alternatives.
I don't think Microsoft building Office for Linux would be a waste at all. Photoshop, Office and Steam games are the big three I see from Linux users complaining about a lack of software. Not all Linux users are fanatical about free software. The question is - what is more important to Microsoft, Office ubiquity or keeping corporates on Windows?