Well, the only reason that Monster Hunter Tri was released on the Wii was because the development costs were too high on the PS3. I'm assuming that the development costs for the NGP will be higher than those of the 3DS, so it would make sense for Capcom to make an MH game for the 3DS over the NGP if possible.
That being said, the MH games released here in America have tended to only sell about 400-500k copies. I'm not sure if Capcom wants to take a huge chance or not. If Capcom reformulated MH just a bit to make it more accessible, I'm sure that it would sell well here in America. Otherwise, MH will be relegated to the "sort of a success" type of game. Possibly profitable (500k copies sold per installment in NA), but not really a blockbuster.
EDIT: In terms of worldwide sales, Monster Hunter Tri underperformed compared to the PSP/PS2 MH games, right? (2 million of MH3 vs. 4 million of MH3P) I kinda' wonder what Capcom's expectations were.
