It is open source software - right? Why aren't there any homegrown releases for these updates that bring them to your phone before your carrier does? Or, am I missing something?
Every major Android phone is likely to get the update, but it'll take time and betas.
//EDIT: In many cases, the homebrew community DOES provide ROMs before the carrier. The Samsung Moment, HTC Hero and HTC Droid Eris were all given Android 2.1 by the community before their respective carriers pulled the trigger.