I know a few years ago japan had problems with people importing anime dvds(What with us not trying to charge $80 for two episodes and all) and some companies actually made it so we got lower quality versions to discourage it. But I can't really see that parallel with games. The price difference can't be that big after import fees and you have to wait months for it..and then it's in another language with EXTREMELY rare dual language exceptions(My one import was a impossible to find Phoenix Wright before it got a reprint, though it really wouldn't surprise me if the US version took out dual language, not on request from japan, but just because that's the kind of thing we do). I just don't see it really impacting business in any appreciable way.
Maybe I'm thinking with too much a rpg bias though. I wouldn't care what language a mario game is in. But I wouldn't go out of my way to get a cheap foreign version either.