But that's the thing; Developers have no reason to STAY with the DS anymore, now that the prices are much more comparable. So while we will be getting games that were already in development, most projects will just be started on the superior successor to the console. Once one of the bigger franchises moves to the 3DS, we will see a huge migration of DS users. Pokemon will probably be the killer, but I see a few people changing over for Rune Factory and SMT:DS Overclocked...
That's true, Pokemon will definitely shift some 3DSs. I was expecting Ocarina of Time to do that as well but I guess it didn't pan out like that. Maybe an original Zelda game will get the 3DSs off the shelves. Rune Factory 4 and Kingdom Hearts definitely sold me! :3
I do disagree that you think it will be a natural migration of projects. The GameCube lost alot of series that were on it's console when the Wii released, Soul Calibur, Main Resident Evil titles to name a few.