Some analysts want to know why Capcom is bringing Monster Hunter 4 to 3DS instead of Vita. Sony was asked about this, and they don't really have an answer.

"I don't know. You will have to ask Capcom." - Hiroshi Kawano, President of Sony Computer Entertainment Japan

We don't know that Monster Hunter 4 is 3DS exclusive, so other versions could be announced at a later date. For now, the one confirmed platform we know of is 3DS.