A lot of these teams are in the situations they're in because they don't have Charlie Batch. Like somebody above said, Ben has never played 16 games, it's good to know you have a capable, proven, backup already on the roster should you need him.
Plus, I don't think Charlie has any desire to play anywhere else. He could have left as a free agent a couple of times in pursuit of a starters job.
Keep him. He's good for everything and everybody associated with Pittsburgh, not just the Steelers.
If this was baseball, sure, sell high and see what you can get. Not in football.