Shipping sources in the orient have told us that the parts are 'on a boat' now, and will be available shortly.
That is the good news. The neutral news is that there will be no major outward differences between the 90 and 65nm boxes, but the latter will come with a less powerful PSU. The only real difference is that the 65nm versions will have a differently keyed PSU connector so you don't plug the new PSU into the old box by accident.
The bad news? Microsoft is removing the EE/GS hardware because backwards software compatibility is better in software, even if it runs 20% fewer games. This is for your benefit, and if you can't see why less is more, you must be a moron.
Oh, wait, wrong company, there is no bad 360 news here. µ