I doubt that, the Astros are going to make a ton of money by selling out on days he pitches and with Clemens merchandise. I'm sure Clemens has a no trade clause in his contract (does anyone know for sure?).
If not the Astros would probably have to get Clemens ok to trade him out of respect for the guy and he'll probably tell them where he'd want to go. If Clemens were to be traded I don't think he'd go to the Yankees because Cashman told Clemens he couldn't leave the team on road trips he wasn't pitching in and that's one of the big reasons Clemens stayed with Houston.
Plus I think Clemens worked out a deal with the Astros to have them call up his son in September to play a game with his father in the MLB.