If this gen has taught us anything, it should be that consoles can gain a lot of steam later on, a slow start might not mean anything at all.
Then again, I'm unsure of the future of handheld gaming and the role tablets and smartphones will have in it so this is hard to say.
But, no matter what happens, the 3DS is more than likely not "doomed" or "d0med" or anything of the sort. The only thing I can say for certain right now is that it is extremely unlikely to come anywhere near the DS' sales in its lifetime.