Where are you getting the info from - I can't even find the update on the HTC site, just ROMS from last year
the roms are on the uk htc site, dated early think january 2010
3UK have the firmware build: 2.73.771.73 on phone and on htc uk site for 3 uk.
because the build is above all others you may not get the first part of the update, but get the second part to make it to 2.1, why i think its because the build has the bits needed already for it to work with 2.1.
just have to wait for 3uk and htc to get there fingers out there combined arses to give you update.
but when you think about it, if it was not for the hero, which has won loads of awards the htc android phones may not be as well know as they are today, they owe alot to the hero and hero customer base, so they keep you hanging on, ok the phone is abit dated now with all the new ones out there, and they may have to chop bits off the 2.1 upgrade to fit the hero. but they really should pay more attention to there customer base and, all who have supported them over the years, give people the answer's they need not keep hanging them on.
the way they have treated the customer base with this update is a shocking, this may come back to bite them in the future!