In a discussion over in this thread, i postulated about why exactly i think Nintendo will put their next console out right on schedule as it were, in the holiday season of 2011.
1) Evergreen won't keep the console afloat forever in Japan. Now, we know that Wii's slump in the land of the rising sun is due to the current slump of major software releases. Something that is soon to be alleviated (starting this month with Monster Hunter G, actually), but i think this proves that Nintendo can't keep the console going for a very long time unless 3rd party support swings more severely in their favor in the long run. Nintendo could try to hold on in the long run, evening things out with European and North American sales (and maybe sales in other markets), but it would be to the great detriment of their Japanese strategy, barring any unforeseen changes
2) According to Miyamoto, they are taking the coming DTV transition in Japan (scheduled for July 24, 2011) very seriously. Despite their apparent advantages, they don't want to get completely left behind by technology. Now, it is definitely true that no fundamental incompatibilities will result from the DTV transition (Wii works on HDTVs, after all), but it seems that with the Japanese going there, America having already gone there by then, the time will be ripe for them to step forward into the HD age.
3) Between backwards compatibility, a 3rd-pillar sort of strategy like with the GBA and DS, they can ease in the North American and European markets that are still very receptive to Wii. The process of upstreaming, similar to what they are doing by migrating the Wii Sports folk up to Mario Kart Wii and beyond, they can migrate the Wii users on ahead, by creating an experience that is unique in their next console, something that brings the immersion experience a step forward, and attracts new users, thus avoiding the potential damages of a market split.
I think it would be folly for Nintendo to follow conventional wisdom and hold on to Wii as long as they can, precluding any movement forward. Not following conventional wisdom is what got them here in the first place 
Monster Hunter: pissing me off since 2010.
