IF, and this is a BIG "IF", Nintendo decided to develop things for mobile phone, it wouldn't go much further than a Miiverse & eShop app and a mobile Pokedex. Maybe a street pass app like was suggested earlier. Those would actually be smart idea's that Nintendo should have already done.
IF, and this is an even bigger "IF", Nintendo were to put actual games on mobile phones, it wouldn't be anything more than a VC app for games from GB/NES TO GBA/SNES, and even then they would still be waaaaaaaaaaay overpriced compared to most software and games found on phones today. But if it joined your unified account and let you play the same games at home and on your handheld too, then maybe the price of admission won't be so bad.
1st scenario may happen, but the second one is only a little more likely than Nintendo developing their own subsidized smart phone, which isn't gonna happen.