I think that third party developers believe that there isn't going to be a psp2 that's why they are giving the 3ds so much support early on. Games like Metal Gear Solid and Super Street Fighter 4 are the type of games that would normally show up on sony's portable before a nintendo one.
But either way the 3ds has success written all over it. The only pitfall that could slow it down is price but I don't expect it to cost more than the Wii did at launch so $250 max.