Apple's tablet is a console, your argument is not valid.
Who knows if this is anywhere near true, but one, assuming the game development environment is the same as the iPhone, this will make DSiWare to look ridiculous, and two, might encourage more development for DSi in a new possible multiplatform development (with PSP as well, even).
Personally, I'm just waiting (and wondering why Apple hasn't done it yet) for Apple to move all these iPhone, now OS X programming familiar developers to Mac game development as well.
I mean, everybody and their dog has come up with the idea of being able to play iPhone Apps off of your Apple TV as a demi-console of sorts.
I don't know. This could be interesting. It could also be nothing. Personally, I don't know where the market exists for a premium Apple tablet. Tablets aren't even very popular with consumers as it is.