While I think Heyman revolutionized wrestling when ECW became "extreme," I agree with a lot of the other posters here that his time in the industry has passed. I watched him though most of his career, and I enjoyed a lot of what he did. However, pro wrestling continues to evolve in many ways (not all, but many), and Heyman's style just isn't the direction WWE is heading.
Yes, he brought the grit back to pro wrestling after the camp and over-the-top bombast of the 80s was starting to run its course. ECW paved the way for the WWE's Attitude Era, which alone gives what he did during that time merit. Now, WWE is in PG mode (well, maybe not after Rock/Cena's "bitch" fest as of late), and Heyman's style was always PG-13 and up.
Yes, during his run as a head writer in WWF/E, he had some really crappy programs. I actually liked him as an on-screen character, even back to the old Paul E. Dangerously days. I'd like him to come back just as a true heel color commentator, since WWE can't seem to establish one anymore w/Cole being so annoying in trying to be the only heelish announcer.
And, like what was said earlier, he's much more into ultimate fighting now and is pretty busy with his Heyman Hustle, so I just don't see him coming back. What's in it for him? He wouldn't be head of creative because Stephanie's in that role now. If he's not in charge, I don't see why he'd come back. Yes, his ego is bigger than it should be, but that's just how he is.
Maybe if Brock Lesnar comes back, he'll tag along. But I see both as highly unlikely.
Move along, people. Move along.