All this talk of Castlevania inspired me to look up the games. They really haven't sold well :(
My favorite, Aria of Sorrow, is arguably the best GBA game and it didn't break 300,000.
Anyway, back on topic, if I was an executive at Konami I don't think I would bother making the game for Wii U. It's just a risky proposition. Although they could have some fun with connectivity between the 3DS game and the Wii U version...something like the relationship between Metroid Fusion and Metroid Prime.