Seems plausible. The team has some good players and they can offer him the deal he wants.
That said, even though Houston isn't exactly a bottom feeding team, I'd have to think if Posey wants to put himself in a situation to win that is not the ideal situation. Houston has proven nothing except that they choke in the playoffs, and the playoff road is tough enough in the West. IMO, Bartlestien just uses this for negotiations, but I'd still see him taking slightly less to go to any number of teams (C's, LA).