John Cena, Randy Orton, Edge, John Morrison. These are some main-eventers on Raw that hardly ever get boo-ed. Edge has his moments as a heel but lately ( with the exception of spearing Bourne after the match) never gets boo-ed. The only real heel's would have to be obviously Sheamus, Wade Barrett, and Chris Jericho ( pending he doesn't retire)
Sheamus is a heel and really hard to see as a face. Although he is a good one one man can't really do it all by himself. Chris Jericho is a good and experienced heel but if he does actually quit then it would be down to one.
Edge-- Edge would be the best case for a heel. He has pretty much been a heel most of his life after E&C broke up. Yes he has been a face but more a heel. This is realistically what will happen since he is already a borderline contender.
The Miz-- Since this rivalry with Daniel Bryanson Miz has kind of not been in the picture as much. If Miz can cash in the MITB at Night of Champions then we can officially see a pretty much all lifer heel in the main event again.
Nexus-- This may not happen but I can see the Nexus breaking up and turning the main eventers ( Barrett and Justin Gabriel) both being faces with the rest being mid-card heels. If this doesn't happen then Barrett will probably stay as a heel and continue to go to town on people.
With the switch to SyFy on Smackdown it is hard to tell who will be switching shows and who will stay. So bleacher community does there need to be more main event heels? If so who do you think they are?