We are probably looking at an inevitable HHH-HBK feud at some point. My guess is it will be the big program through the summer and culminating at Summerslam. It's been awhile since they've locked horns, so I wouldn't be against seeing that at all.
In the meantime, HBK-Orton is a big time feud for Wrestlemania, and I think HBK will probably go over to get the best of Orton since he was the man that put him out of action.
HBK will never be on Heat or ECW....hell, he will never even be on Smackdown. I think he is still a huge talent, it's just depends on how hard the WWE is going to push him. I'm not really seeing a title run for him anytime soon.