I don't use Linux apart from the occasional live CD to trouble shoot some problems (although I'm rather liking some of the new builds I'm seeing and wouldn't mind going for a quad boot
but thats another story.)
That said, just logically speaking, I don't see any reason MS would shut down linux skype. Further development may be unlikely, especially considering what you guys are all saying about how skype hadn't been updated on linux for years even before the buyout, but that doesn't really change anything.
I also see no reason why they would shut down steam on android.
Yes, android competes with windows mobile, but MS is not adverse to other platforms paying for their services. Apple uses Microsoft Office after all. Its all about getting money off those subscribers.
As for loss of revenue from not updating the client for linux... does the current one not support calling landlines? The Linux home pc community is pretty darn tiny. I figure MS (and skype's previous owners) figured why update when it works ok and there are very few if any users that would pay for it if it were updated but do not pay now.
Keep in mind, users just using it for pc-to-pc VoIP aren't the ones making big bucks for MS/Skype. Its the people using skype to call landlines.