I assume that Microsoft is making some money on Office for Mac. They aren't developing that product for charity. I don't see any reason for them to kill off development for the Mac, especially if they acquire Adobe.
Microsoft could use some help in the mobile market, though, so I can believe the idea of those two companies joining forces to make some headway there.
Vendor lock-in isn't as crucial to Adobe's CS as it is to Office. Microsoft doesn't want anybody to even think that there's such a thing as an "Office alternative", whereas recent years have proven that upstart competitors to components of CS can get traction.
So, while killing CS for Mac might work (users switching platforms might outnumber users switching programs), killing Office for Mac would just force universities to switch to ODF and in the long term, it would hurt the rest of Office's markets.
IMHO that would be a catastrophe for Apple: the existence of MS Office being the only reason Mac OS X (and not Linux) is an accepted alternative for employees inside many companies (including at Adobe btw).
Sorry, but CS is niche software used by certain professionals. MS Office / Exchange are used by everybody else ;)
And I wouldn't bet against Microsoft for providing an alternative to CS: judging from the experience of using Microsoft Blend, they are rookies, but they can manage it.
