Not so sure about the issues between Sense and 1.6 being resolved and it being ready for release. If that were true why is it also not available yet for unbranded unlocked GSM versions of the Hero?
I think they are just waiting for 2.0 - given the short amount of time between 1.6 and 2.0 why bother releasing, and potentially introducing more issues with, multiple releases.
Hopefully they are doing their best right now to get 2.0 working as well as possible and will be able to release that as soon as Google give them the green light (after the Droid release?)