Wired interviewed Miyamoto and here's a portion of it:
WN: Getting off this subject, can you tell me what’s going on with Wii Ware? It’s been announced, but we haven’t heard any details.
SM: Wii Ware is something that we’ve had planned all along for the system, so even though we’ve just announced it it’s not something that’s very new for me. But, our group isn’t specifically focused on developing any Wii Ware. But we have in our internal development teams who are constantly doing different experiments and will have different ideas about games. And oftentimes a lot of those experiments can’t be fully fleshed out into, say, a Mario game or something like that. But those individuals will often want to find a way to take those ideas to market. So it’s possible that we might be able to take advantages of some of those resources and turn them into small and compact Wii Ware games.
But really, I think the advantge of WIi Ware is that it allows a lot more freedom — they can take something that’s a much smaller concept or idea and turn it into a game that they can present to the public. So I think it adds another layer of freedom for the developer.
WN: Tell me more about Wii Music. I thought maybe that game would be a shoo-in to get shown at E3.
SM: We had a few too many titles to show off this year at E3, so we decided to hold that one back. I think it will be another big step forward in terms of Touch Generations style games for Wii, so you’ll just have to wait until we can talk about it.
WN: Is that still on for this year in Japan?
SM: I kind of focus on games in order, one by one. I’m focused on these right now. So I’m thinking Wii Music might be good for next year sometime. Mario Kart, as well.