2013 or 2014 (I'll plump for 2013).
TBH, unless we see only a modest jump in specs, I worry developers would be in trouble with too quick a move. So many games today aren't even 720p and yet many developers are saying HD titles cost too much to develop vs risk for high sales.
I'd like to see a long gen, with a focus on better and better SDK to significantly reduce development costs before we see new consoles.
Note, given the difference in cost I do think Nintendo could bring out a new console sooner if they wanted, but Sony and MS? I think they should look at sales of Wii, look at PS2 and stick with their current consoles and focus on expanding them via motion controls, etc. - which is what they seem to be considering.
Try to be reasonable... its easier than you think...
