I think it is going to come down to singles and promotion with the battle between U2 and Eminem. I don't think that Eminem is quite as popluar as he was last time around. I think his debut will probably be around 750 to 800, 000. But this could change if his single completely bombs or completely explodes. A huge success for a rap single played all over both rap and top 40 stations would be enough to easily launch him over a million the first week. U2 on the other hand could have Vertigo become a huge hit on modern rock and rock radio, and probably get some decent play on Adult top 40 and some on top 40, which would give them a solid 450 to 500, 000 for their first week. If it bombs (which it doesn't look like it will do at this point) It could mean barely hitting 400, 000.
We also have to take into consideration that because we will be nearing Christmas that the second week sales of Eminem will drop less than if it were a non-holiday time. Sales remain strong and consistent throughout the lead up to Christmas. So his sales could possibly only drop 30 to 40 percent the second week as people hit the stores in bigger numbers.
All in all, my gut is telling me that U2 will be blocked from number 1, with Eminem opening at 800, 000, going down 40% the following week to 480,000, and U2 hitting number 2 with 440,000.
That's my best guess at the moment.