Seems that the green light has been shown for the US to receive Mango, which ties in with recent reports from Sprint and other operators. We expect to see the rollout gradually reach everyone so don't freak should you not receive the notification immediately. For those who are on builds newer than NoDo, be sure to have backups at hand, especially if you're on leaked RTM. Be sure to let us know when you receive the update, good luck!
Note that on AT&T: "Delivery has begun for the HTC Surround, LG Quantum, and Samsung Focus v. 1.3. The HTC HD7S is currently Scheduling, while the Samsung Focus v. 1.4 is Testing and the Dell Venue Pro is in Planning."