Neh that's pretty much incorrect if your implying the PS3 to Xxbox 360 move as Xbox had a larger install base world wide, and they ported itin order to advantage of larger worldwide install base which the Vita doesn't even have. Was DMC ported to the gamecube, same wih many others.
X360 IPs went multi or ported to PS3 when 360 had a bigger user base.
SNES went multi or ported to Genesis/Sega CD when SNES had a bigger user base.
DMC went from PS2/PS3 exclusive to multi when PS3 wasn't even released.
Mega Man Legends was even ported as PSP launch game.
Capcom is not interested in the failure that is the Vita. They release their games on successful consoles where their games will sell. I don't think they would have released on the Wii U, either, if it wasn't for Nintendo moneyhatting them.
It wasn't only Vita or WiiU, Capcom also strongly supported devices like Dreamcast or Saturn when they knew their install base was small.
Honestly. Why release on Vita? Straight forward motivation for them to release MH on Vita?
Extra revenue from a cheap port as Capcom typical does (see SFIV3D or UMvsC3 Vita), and to don't have to worry if a device sells more than other in the future. Specially if some release of games like this and a pricecut revives sales as happened in 3DS or others. It also would help with their rellationship with Sony, which would help Capcom in next gen home console games.
Multiplatform has been a win-win situation for Capcom always, and if they didn't implemented in portables was because DS wasn't capable technically. Which all these home console IPs on 3DS proves.