the update prolly wont happen for another few weeks at the earliest.
2.1 will be open sourced in a couple of days.
That's the android base code though, individual manufacturers will have to include software for the actual hardware (like bluetooth/wireless/LEDs), then from there it's up to the service providers to push the updates out to retail handsets.
If you're on an ADP or rooted device, you can build your own firmware soon. : )
I figure around the 15th people will start getting updates, with the goal being everyone updated within 7 days. That's the rumored date (22) and that's how 2.0.1 went.