With Jericho off RAW, JBL "done". And Batista and Cena as baby faces. And HHH as a face too. RAW needs another main event heel. They've got Orton/Legacy and The Big Show and that's about it.
I could very easily see The Miz hitting main event status. The guy can cut a promo better than many veterans. And his in-ring talent has improved 1000% in the past year. Right now, his ring work is Better than Cena's, Batista's, and DEFINITELY JBL's. The only problem is, I doubt if he'll be able to carry some of the more untalented faces the way only Jericho and RKO seem able to do.
But regardless. What it comes down to is how much heat he can draw. And he can draw more than enough to merit mainevent status.