He won't be able to change it much. The potential retirees are Rehnquist, O'Connor and I believe Kennedy. Of the three Rehnquist is conservative, Kennedy liberal and O'connor mostly conservative though her hormones get the better of her sometimes and she votes the socialist/liberal/gubmint route. It'd be nice to have all three retire but even if that happens it would only swing the court to 5-4 conservative from it's current 4-4-1 makeup. Of the three I don't see O'connor retiring. Rehnquists cancer seems to be being cured and he seems to want to hang in there. Kennedy at 85 is the one I would expect to hang up the robes but as a hard core liberal I imagine he'll try to stick it out until the next election.