I think the software situation in Japan (and situation in general) is what will push Nintendo to a new console by next holiday season. They've got enough strength on their own that Wii can move through the end quite handily (and remain quite strong even in Japan at the very end, as Dragon Quest X is likely to land Fall 2011 as well)
My bet is that Microsoft will match that date for a new console, though, and they too will have the strength to hold 360 through to the end (and not drop it like a hot potato like they did with the Xbox), but Microsoft is going to want to head into the next generation quickly, a super integrated Kinect upgrade console at roughly double 360 specs.
It's Sony that'll hold out, but not past holidays 2012
Monster Hunter: pissing me off since 2010.
