they aren't going to be announced as a new console. In fact they likely won't even be announced right away once they start shipping. It is going to be a silent upgrade, at some point they will just start showing up in stores (no doubt it will be all over the net when it happens)
Yesterday on Engadet (i lost the link, go back a few pages and you shoudl be able to find it) they posted a story that says the 'Falcon-based' 360s are startign to show up. Apparently some of the new Halo 3 branded 360s have the 65mm chips (they listed batch number(s), i guess it isn'ty all of them. I don't recall where the story was posted (i.e. where Engadet got it from) but it seems the 65 chips might already be out there.