Will the upgrade be part of a "disc & box" Vegas anytime soon? Or will it just be by download?

If V4 and V5 are any indication, it will be by download only. All the box set does is give you the hardcopy "Intro" manual which contains the all important Serial Number for registration. They already had 6.0a out by the time I upgraded (two days after release), so I never installed the software from the box set, just installed the 6.0a download and registered it. Downloads of new updates after registration generally go smoothly and do not require re-registration.

It's really a non-issue.