I think it would mix up a bit. I know a lot of older boos would go away. But the fact of the matter is WWE will NOT let Cena change his gimmick, or go heel until they have built up a solid other baby face for the company. I really thought that was their plan with Ryback so they could give him the face title, and let Cena finally expand out to being a heel. Clearly having Ryback go heel completely put this theory to bed. Unless he goes back face, and WWE tries again.