Hmm... some people's guesses make me think that they expect absolutely no tail for some systems. But for total time left on market well, let's see...
Wii: 4.5 years. I don't quite see it lasting as long as the PS2 in the post-gen market, but I see a new Wii for release in 2012, maybe holiday 2011 if things go weird sooner.
X360: 4 years. I see Natal being different enough from what's out there to generate renewed interest in the system. I also predict holiday 2012 for the 720.
PS3: 3.5 years. I think Sony has learned from all the mistakes of the PS3, and will not use them all with the PS4. I see PS4 as being backwards compatible and released at a lower price. The slim margins on the PS3, coupled with reduced interest in some markets, will result in Sony trying to phase it out on a high note, before letting it become the "bargain system gasping for breath."
-dunno001
-On a quest for the truly perfect game; I don't think it exists...
