Nintendo is rather apathetic towards the GC, unlike Sony and their PS2.
An example of this is the upcoming Spider-Man game (
*gasp*, Spider-Man 3!). It's coming out for all the next gens (The Wii, PS3, Xbox 360), but it's also making the cut for the PS2, yet not for the GC. This is
not due to lack of power. The GC could easily play Spider-Man 3, but Nintendo is content in letting a great console die. The PS2 is still having a lot of games, just look at the games already released this year <
link>, and there are a lot more coming out this year.
The GameCube was great, the controller was great, and from what I've heard, the SDK (Software Development Kit) was easy and intuitive. However, Nintendo is burning bridges by going only with their Wii. Too me, this shows a lack of customer loyalty. If I have a GameCube, I have to immediately buy a Wii or suffer with old, stagnant games? The counter-argument may be that the Wii can play GameCube games, but so can the PS3, yet it's still being developed for.
No-one's making the point that the PS2 should still be kicking around months from now, and don't even think of making the point that Sony is just sitting with old, cheap technology (just look at the PS3 for the exact opposite!), but it's customer loyalty. People can easily slide into the next generation, and Sony gets to make money on an already established market.
I think this is a poor mood in Nintendo's part, but at least the GC names will still be playable in the Wii.