A lot of people have pointed out that releasing a system comparable in specs to PS360 and trying to attract developers because of the smaller development costs is the exact same strategy that backfired with Wii's lackluster third party support. The circumstances are a little different here, though. Wii came about late in the game, after major publishers and studios had already made the big investment of upgrading to HD development. Furthermore, Nintendo were coming off the GCN back then, so their influence in the wider industry was at an all time low. This machine is coming while the industry is still very much in PS3/360 mode and is the successor to the fastest selling console ever. If its gimmick/distinguishing feature is appealing enough to drive adoption at even 2/3rds of the rate Wii sold at, then third parties are in a very interesting position. I suspect that Nintendo's argument that it would be better for most to continue developing for the combined PS3/360/N6 userbase than make the leap up to more powrful hardware, especially when adoption may well move below expectations (look at how long it took for PS3 and 360 to accumulate total sales numbers higher than the Wii alone), would be a hell of a lot more compelling than last time.
If they play their cards right, they could drag this gen on for a very long time, until the industry has 'expanded' more and their ready to move on. Sony and Microsoft's next offerings might look irrelevant and overpriced to developers and consumers for many years. It's Nintendo's version of 'next gen doesn't start until we say it does'.
If this thing really catches on, all bets are off. But it's a big gamble.