First, I think you mean 1.2 v. 1.5, not 2.2 v. 5.x.
Second, Wordpress 1.5 was released today. You can't expect DH to have a custom distribution ready for use the very day the software is released. Give them a little time to package the new version for their one-click system and test it for problems. I'm sure it will be available before too long.
You can always download and install it yourself if you're really that impatient.