You mean the ones announced today?
Even though they are on the Apple Store, I clicked through the purchase process for the Power Mac G4 733MHz, and got an estimated shipping time of 7-10 weeks, so I don't think you'll get one tomorrow.
That said, as an Apple Development Partner, we do have them in our testing department and as always hope to qualify them as soon as possible. There's no way to give an estimate of when that process will be complete, especially given all of the additional and concurrent testing involved with Pro Tools 5.1.
But thanks for asking, I think you were first!
------------------
Bruce Paine
Digidesign