I doubt he would be a gold glove thirdbaseman, he doesn't have the arm for that.
In any case, he's a great utility player, but we have had plenty of those come through the organization over the last decade, and there are always new ones to be called up. I think the argument made upthread was more of a "you have to give something to get something," and Dubon is certainly valuable as a trade piece. His value is considerably less for the Astros when the team is healthy too, which we hope (fingers crossed) none of the starters begin the season on the IL for a considerable amount of time.
So if he can be a piece of a trade that nets the team a better player, or adds some bullpen depth, why not? The Astros shouldn't have to rely on someone like him in the playoffs, his role should be the 10th man so to speak, but there are plenty of guys who can do that during the regular season. It doesn't have to be one guy backing up 7 others, that's why you have 26 active roster spots.