Why is Clark still in Smallville?

Is it because the name of the show is Smallville that Clark is still in Smallville? Have the producers already decided that as soon as Clark makes the inevitable move to Metropolis, the series is over? Clark said at the beginning of Season 6 that he was moving to Metropolis. Move already! It coud provide for some more "interesting" story lines than what we've seen up to this point, to say it nicely.