I would imagine that if Konami wanted to make a 3D Castlevania, they'd make it for 360 and/or PS3 where the hardware is far superior. That, and Iga has said before that he wouldn't be fond of a heavy motion-control in a game.

If a there's one for Wii coming, it'll most definitely be a 2D sidescroller, and a lot of rumors are pointing to a Wiiware release.