Both GBA versions
Both versions of Mega Man Battle Network 3 (Blue and White) have been rated for the Wii U eShop by the Australian Classification board, which of course highlights an impending release. Why Capcom would release the third iteration of a sub-franchise before the first two is unknown, but it stands to reason that they're gearing up to release the first three, at the very least -- this is just the first sighting of it.
Capcom has promised that it will start delivering more [old] Mega Man games to the 3DS and Wii U eShop, and it appears as if they have more up their sleeves than the other releases they announced earlier this year. Of course, we're still waiting on Mega Man V and VI on the Wii U over a year later.