I think the only turn that should be made now is Shawn Michaels (he's pretty much int the middle of his turn now) after his recent promos he could play a mentally disturbed type character, we've already seen that from his devastation from his recent failures.
Randy Orton, imo should stay how he is, I think his face pops would go if he actually turned, and putting up against heels all the time would get boring for me, because he is better against a face and I find it funny that someone could be in ultimate face mode with amazing face promos and they will still not get the cheers they were after and Randy will get amazing cheers.
John Cena is in full on face mode and getting some of the best reactions of his career with this Vince/Batista storyline, it would just be a massive buzzkill to turn him heel now imo. Perhaps, in a year or so (probably longer) when his massive crowd reactions have died down but I can't see it happening just now, it wouldn't be credible, we need to be eased into it.
Triple H imo is could look better face now than he has done in a while, even when he had his feud with Orton. Not because of DX (maybe a little bit, but in a different way to usual) or because he's back in the title picture but because he could just not give a shit Shawn Michaels could be doing all his heel shit and Triple H could just give it a little reaction and get on with his matches. I would like to see him not even feud with HBK after they split up instead just go out and wrestle (maybe win a title). It would be even better if Michaels went into massive heel mode and HHH could just not pay any attention and still carry on with DX with HBK still in it, they could do all there normal DX shit and HHH would be clueless, I would lol so much, it wont happen but I would love it to.