I'm going to go out on a limb here and say that Justice Scalia is going to be the next Chief Justice of the Supreme Court. We all know that Chief Justice Rehnquist is not at the top of his game, and rumors have him retiring by the end of the year. Justice Scalia has the benefit of being one of two Justices currently under 60, which means he'll be more able to stick around a while. He's also one that President Bush is apparently fond of. I know, I know, I'm repeating what several others have said. I don't have much to offer there.
Over at the University of Pittsburgh School of law (http://jurist.law.pitt.edu/mentions.htm), there is a list of possible replacement justices for whomever becomes the next Chief Justice.
One name I didn't see on that list, but I have heard as a possible dark horse is former Texas Supreme Court Chief Justice and current South Texas College of Law professor Tom Phillips. That could be an interesting name to keep in mind as this plays out. Other names I've heard more than once include J. Michael Luttig, Edith Jones, and Alex Kozinski. I also would find it interesting to see Judge Posner selected, though, that could be a long shot, as well. Anyway, I'm no expert, and if I put enough names on here, maybe one will get selected and I can say "I was right!"