He's not that great of a prospect, nor is he that young anymore at 23.
He started just three times this season for Bayern so far, and with all the competition he's got there I doubt that will change in the future. In general, I don't think he'll ever develop into a player that could start for a side similarly strong as Bayern are right now.
His contract is running out in 2016 and he's unlikely to extend it. He wanted to leave in the summer but Bayern decided to keep him. He's still unhappy with playing time he gets and he wants to leave. I think there was a recent quote of his stating something like that in the wish list thread.