Evan Wilson, an analyst with Pacific Crest Securities, says there is a new Nintendo DS being designed.
According to Wilson citing an unamed source, the new hardware will drop the GBA slot have an even thinner profile than the DS lite and add some storage media and enlarged screens. Reportedly, nintendo is waiting to release the new system until demand and sales for the current-gen DS lapers off.
Hmmm... keep in mind, it's just a rumor now, but it seems pretty likely that Nintendo would have at least begun design on whatever they have coming up next.