Why is it so important that Hogan be at WMXX? It's certainly not going to be the last one (and anyone that believes TNA will overtake WWE are very much mistaken) and his return would only hamper the development of the younger talent on the roster. Wrestlemania should be a venue for the Eddy's, Benoits, Angles, hell even HHH, Orton, RVD, and whoever else has been on the roster full time.
Vince does not need to, and should not cater to an over the hill wrestler that frankly walked out on him.