If you really are a Christian, you'd realize that President Bush has as little control over SCOTUS justice seating as he does the tides. Short of death or disabling circumstances, there is no way under the sun a liberal justice will retire to knowingly allow a "conservative" nominee to potentially take his/her place. The health and life of those justices are in the hands of the Good Master - not Pres. Bush and it is only He who grants the President the influence over the courts.
Believe it or not, the justices have themselves politicized the SCOTUS makeup by delaying their inevitable "retirements" to occur only when the nominating executive may hold similar convictions to their's.
I think you're right. I can easily imagine the left-leaning judges hanging on for at least another four years.