It'll be when he feels it's ready. I think the only reason he hasn't played it is the karaoke version for his prompters wasn't ready yet. We all know the perfectionist he can be sometimes. I only know this, because that's what he said at the soundcheck in Chicago where he sang it twice. I think they are still tweaking the orchestra arrangement on it as well.
Or who knows, maybe he's just decided the concert is already long enough?
Here's hoping by Milwaukee!

Though I was still hoping he'd spring a new song on us there.

:-] OK, not banking my life on that one, but wouldn't that be a pleasant surprise. Just surprised there are any tickets left, even if they are the ones way off to the sides.