Capcom currently has no plans to release Monster Hunter 4 on the Vita, according to Siliconera's translation of Mainichi Shinbun Digital's interviewwith Capcom COO Haruhiro Tsujimoto last week.
Tsujimoto explained that Capcom wants "to have as many people as possible play it on the 3DS, and we are only thinking about making it succeed." Tsujimoto cited a "limit to how long something can be continuously developed on the same hardware" as a reason for the switch up between Sony and Nintendo's platforms.
When he was questioned about developing for the PS4 and next-generation consoles, Tsujimoto's thoughts seemed to clash with their strategy for Monster Hunter 4: "While planning out game content, we will develop and judge which hardware is the most suitable. However, for the sake of the players, having it be a multi-development is the most ideal."
During the same interview, Tsujimoto stated that Capcom hopes to sell 2.8 million units of Monster Hunter 4 in seven months. Considering they managed to move 1.6 million copies of the Japan-exclusive Monster Hunter Tri-G for the 3DS, finding 2.8 million players to slay a fresh pack of monsters with enormous weapons might be a cakewalk.