I always receive a “You’ve been upgraded!” push notification if I checked-in via the app and right after I receive the “Your room key is ready. Step by the front desk to collect it” push notification (and, of course, if there was a room upgrade to begin with).

At this point the upgrade, if any, should be final. However, there are plenty of DYKWIA guests out there, and if one of them happens to checkin physically before I do there’s definitely a chance that just of exhaustion he’ll get a front desk associate to reassign him my yet unoccupied upgraded room.