I don't think that Bayonetta will go multiplatform since Nintendo is funding it. Unless a first party like Nintendo funds a game or it uses Nintendo properties in the game I can't see why any third party would want to remain exclusive to one console. It makes no business sense.
Having said that.. There will be a plethora of 3rd party wiiu exclusives but these will be games they made together with Nintendo and use Nintendo charctertics in them like Smash Bros ect.