New hardware is introduced whenever the experiences from the existing hardware are becoming stale. That has always been the way in gaming: Software sells the hardware.
Developers have yet to utilize the full potential of the DS. With the addition of camera and music features in the DSi, there are more gameplay possibilities that can come out of those. Hence you will likely not get a DS2 in the near future.
On that note however, I think Sony should make a major revision with the PSP since the experiences from it is mostly the same experiences from the PS2 and PS3 (albeit portable.)







