I think Sheamus ends up filling the role HHH used to play. He can be a dominant heel, carry on whole conversations with just his facial expressions, get over as a face, but his character's actually a natural tweener who can be a chameleon so far as his role is concerned.
CM Punk is filling the role that Austin basically originated, being the anti-authority anti-hero face. He's got a similar mic style to Austin, just edgier.
John Cena is the modern Rock. Basically, he's got a lot of heel characteristics and he's the kind of guy that people love to hate, but he's got the right type of natural charisma that he just gets over.
Bryan is the new Jericho. Smaller frame, can work a variety of styles, good on the mic, can get pops or heat. But he's going to be more comfortable as a heel (and he's probably going to have more fun that way).
Rhodes is the new HBK. Tremendous amount of athletic ability, good mic worker, irreverent humor that can go over the top. And once he turns face, it's going to be hard to turn him back.
Ziggler is the new Edge. Very similar style to Rhodes, but it's going to be hard to maintain him as a face. His natural inclination and personality fit a heel persona too well for him to stay over as a face for very long. And, even when he is a face, he's basically going to be an "anti-face".
Ryback, from what I hear, is going to be built a lot like Hulk Hogan was. He's going to be Superman/He-Man/Face with a look very similar to Goldberg, but better in-ring skills. In a lot of ways, it's not going to matter how good he is on the mic, because it's going to be directed to kids (Say your prayers and take your vitamins, brother!)
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