I'd imagine all retailers will get more than enough copies to cover pre-orders and beyond. We ain't talkin' X360, here.
I live in St. Paul, MN and have called a bunch of GameSpots, EB Games, a GameCrazy, and a couple Best Buys and Targets in the Mpls/St.P area. Everyone is saying the same thing: The game is shipped today and they'll have it tomorrow.
I don't know if it's true, but I'm not in a position to know what's what.
Right now the best thing to do is to wait until 4 PM or so and make another round of calls. My guess is if they're actually getting it today, they'll know by then. But again, I don't plan on getting it any sooner than tomorrow afternoon here in the midwest.
I'd love to hear from other people on this.