I think now's a good time to move Calderon. He's not going to get better than what he is showing right now. Plus, he's performing up to his potential- able to rack up an efficient double-double game- without the injuries. If we are going to get the most value for him, it would be now.
And I'm with Claudius, we don't need a returning point guard. At this point of the season, it is evident that we are not competing this season. We might as well get a better option at point guard during the off season with a go at free agency. In addition, it doesn't make sense for a team to give up a point guard to get Calderon; any takers for Jose would probably look for help at the PG position.