If Sony and M$ don't follow Nintendo's lead with delays of their console sequels -- this will be a huge mistake. Nintendo's line-up this generation has been nothing spectacular, and even though people are buying GCN now, that doesn't mean that those sales will continue, especially for three more years.
In my opinion, the software this generation has not had the Nintendo touch. If I had known the quality of some of the big-name GCN software (i.e. Mario Sunshine, and to a lesser extent Zelda) before the system came out -- I might not have bought the system. I loved Nintendo when they made unbelievably great games. But they have some how managed to lose the knack of producing great games. Mario Sunshine pales in comparison to Mario 64, GCN has nothing to even compare to GE or PD! There have been no great multi-player games for the current console; SSMB:M was decent, but, like the Marios, I still prefer the original. TS2's multiplayer was alright, but it wasn't exclusive and GCN's wasn't the best version of the three. And besides that, if I'm gonna play a FPS with some friends I'm gonna play Halo, and later on Halo2 and PD0 (on the Xbox!!!). TS2 can't shake a stick at Halo. Nintendo's current and announced software lineups just can't sustain good sales for another three years! Plus on top of all that 3rd parties have already started to jump ship.
The gist of this rant is this: Unless Nintendo makes some major changes in its software development philosophies, makes games as good as they were last generation and attracts more development houses to their current system -- there is no way that this system will last three more years.
P.S. keep in mind I didn't even mention online gaming!! Just imagine where online gaming could be in three years....and Nintendo will still be stuck in years past, forcing single-button games upon people and demanding that online gaming is not what gamers want!