We've been receiving numerous tips over the last hour that Nexus One owners on AT&T bands are receiving an over-the-air update for Android 2.2 FRF85, otherwise known as the "bulletproofed" Froyo build. No confirmation at this point, and since you're asking, no word yet either on an update for the larger T-Mobile N1 install base (though we've had at least one report of a user on FRF50 getting the OTA today). We've pinged Google for answers, will let ya know what we here.
