Theres a limit to how long something can be continuously developed on the same hardware, Capcom COO Haruhiro Tsujimoto said in an interview. The Monster Hunter series started out on the PlayStation 2, then on the PlayStation Portable. Monster Hunter Portable 3rd [which was a huge hit] had reached the end of the line, and in order to meet new expectations, it was required for us to switch platforms.
Games have ideal release periods, which also determine when their development begins. This resulted in our judgment of seeing the 3DS as the most desirable [platform for Monster Hunter 4].
We want to have as many people as possible play it on the 3DS, and we are only thinking about making it succeed.