Ok, let's review some things:
-They already have an engine for all the consoles.
-They can reuse the assets of the previous KHs on the Wii
-They need less time and money developing the game for the Wii
-Epic Mickey just prove that Third Parties big titles with a big Disney Mascot can sell a ton on the console
For me it makes perfect (financial) sense to create a KH for the console, maybe 3 maybe another non-nunbered game.