Surprisingly Motorola/ATT seems to be on the ball with 2.2.
I'm not expecting 2.2 for Evo at all. Even if official OTA 2.2 is released in the next 5 months, enthusiasts would be 1) Already on non-official 2.2 and better/cleaner ROM, 2) Moved on to other devices. Average Joes will go on merrily and ignorantly enjoying 2.1 until they qualify for an upgrade.
Just chalk it up to cell carriers continuing the tradition of de-prioritizing OS upgrades and focusing on upcoming phones. Sprint got you for two years, else termination fee, else re-up contract with new device. Enthusiasts, who make the most stink about OS upgrades and other issues/wants, make up a small minority.
If HTC/Sprint 2.2 is gold next month, great! Early Christmas then! Else I'll hold out for Evo2 with GB in 2011.
