I think we often downplay how much goes into being 'The Next Face of the WWE'. This person really needs to be the perfect storm of physique, mic skills, passable wrestling ability, and personality. Based off this criteria, I have to respectfully disagree with a lot of these suggestions:
Ryback: He can be a top player, but definitely not the face of the business. He's too poor on the mic, and his personality has little flexibility. Guys like Austin, Hogan, Cena, and Rock can be funny, intense, passionate, good, bad, or in-between. A guy like Ryback, just not that versatile.
Cody Rhodes: He's got a bad lisp. I'm sorry to call it out. But the MAIN guy who promotes your company (at charity events, on Late Night Shows, and beyond) needs to be an awesome speaker. HHH was never the face of the company, and Cody Rhodes isn't 1/5 as all-around talented and a stud as The Game.
Punk: If it weren't for his age, my vote would go to Punk. Amazing on the mic, massive ego and personality, loves and gets the industry, and a stud in the ring. But, when I think of the next face of the WWE, it's hard to think of a guy who is almost 35. It's the same reason I won't put Ziggler in my list, despite the fact that I think he's the total package.
Daniel Bryan: Physique. Short by wrestling standards. He's getting a little chunky and until he shaves that beard he can't be the #1 guy in the company.
Dean Ambrose - OR - Seth Rollins (not Reigns, see my take on Ryback for reasoning): These two both remind me of Punk, but a little fresher. They are both solid on the mic, awesome in the ring, and also seem to love and understand the industry. I feel like they both bring unique styles to the WWE. If I had to pick which would have a more successful career, I'd pick Rollins because I think he has more babyface potential than Ambrose. But hey, Mankind, a guy who wore a mask and stuffed socks down throats captivated an industry as a good guy for a few months - so what the hell do I know about good guys and bad guys.