Going by ATLUS USA figures (which can be found here: http://www.siliconera.com/2009/10/06/well-how-many-copies-did-persona-4-and-devil-survivor-sell/), Persona 4 sold like shit in North America. Only 110,000 in the fiscal period of Aug 08 to July 09. Whereas it sold 300,000 within that same period in Japan. So the western market isn't all that important for Persona.
They'd be better off releasing P5 on the PSP. It's much cheaper. They would have to sell a lot more on the PS3 or PS3/360 to recoup the investment necessary to make a HD Persona game. Also Persona 3 Portable sold about as well as the PS2 version did (which has a much larger install base than the PS3 and 360 combined in Japan).







