The story I heard is he asked Houston to release him and they obliged as a favor to him. That is why they did not trade him.
I also heard he wants to go to a team with a chance to make it to the Super Bowl. He is from Wisconsin originally, so maybe he is eyeing Green Bay and Aaron Rodger?
People say Pittsburgh, but what if Rothlisberger retires, which has been rumored as well? Would he still want to go to Pittsburgh with an unknown QB?
As for the Cowboys, people who say JJ Watt is finished are probably close. I think he has a year or two left in him although injuries are a big concern. Maybe he wants to stay in Texas, but if that were true then why not stay in Houston? I am guessing he either wants to play with his brother in Pittsburgh, or go back to Wisconsin. Then again, it would not shock me to see him in Miami or San Diego.