Again, the problem is we are dealing with HTC and Sprint. With a limited track record we have no idea how long either will take. Whether or not the Hero took as long as it did due to technical issues, incompetence or corporate strategy (or lack there of) we still don't have enough data to make an accurate guess.
BTW with peoples supposition that the Hero took so long to move from 1.5 to 2.1 due to the hardware I would disagree. Look how long it took the Euro Hero to move over. About 12-13 months and I do believe the hardware was similar, albeit, GSM. This tells me that firmware releases are all about money not specs.
With that said, I will laugh my a$$ off though if the Incredible gets 2.2 before the EVO though. If that is the case, so much for the statement that the EVO will the the "second" phone with FroYo.