Houston's motivation in getting Beltran was to try and get back into the race. That didn't happen, so now their motivation to trade him would be to get something instead of losing him for nothing.
As for Clemens, I can see him possibly asking to be traded to Boston or NY to get back into the race. In fact, if Houston bails on Beltran, Clemens just might hang 'em up.
Trading Clemens would be done as a courtesy by Houston, towards Clemens and they wouldn't get much of anything in return. Besides, Clemens can always resign with the Astros next year if he chooses.