Still kind of confused about this upgrade. There's presumably going to be software that uses the camera, and software you can only play by downloading, so like it or not they split the user base.
Since that's the case, why not just come out with a more powerful DS2 with these features? My only complaint with the current DS is the hardware is showing its age. Boost the resolution, up the ram and processor speed, basically do a Gamecube->Wii style hardware upgrade. Keep backwards compatibility and you're done.
I guess they're just following the old Gameboy line of products, meaning the DS won't get a major overhaul for another 5 years :S