Ryback will probably be a big star, but I also don't see him being the face of the WWE. He has the cosmetic look and with the right booking and marketing, the WWE can help get him over as a star in a Goldberg-like way, but he doesn't seem like he'd have the charisma to be the face of the company for the next 5-7 years or so.
To be honest, I don't see anyone on the current roster being it, unless one of them happens to do a complete personality/gimmick change and surprise the hell out of everyone (it can happen, no one would have ever thought The Ringmaster and Rocky Maivia would have turned into Stone Cold and The Rock in such a short time span) but most likely, it'll be someone who hasn't debuted yet.