Let's have another go at it:
"the current systems have basically reached their limits"
True when speaking of actual gameplay. There's been some interesting views on what Iwata san was thinking when he said this. I'm with Sooper Dood all the way, but I think he's also thinking of what is needed for Nintendo, in order to make the games they like to make.
Mario Sunshine has been accused for not really pushing the system, but if Nintendo is happy with how it is, and believe they can do many more great games with the GameCube technology, why on Earth would they produce a system with four times the graphical power, but no real design related benifits?
The current systems have basically reached their limits... in what new game design aspects they can actually present.
And that's probably why Nintendo is cooking up some mystery device, to offer those new hard-to-achieve revolutionary gameplay concepts. The hundred-NES-games-in-a-controller is a nice thought, but hardly very Nintendo'ish. Iwata san also said last week that the new system will work alongside the GameCube and GBA as "a third pillar," and a multigame NES rerelease doesn't sounds like anything in that direction to me.