IMO even at 8+ years old, for the same money, the HDG2 is still a better scope than the Mark5's, XTR3, and XRS3. And, if it were to fuck up for some reason and I had a match this weekend, chances are more than likely Vortex would make sure I had a working one on my rifle by then (with the others.... not nearly as good of a bet).
Personally, besides just wanting the latest shit... there honestly doesn't appear to be much reason for me (or maybe anyone else) to ditch our Gen2's just yet. It will have to look pretty damn amazing for me to trade probably the most proven scope design of its kind available, plus ~$1000 or so more money... for a brand new unproven design with slightly better glass.
Actually, if the glass is that much better (which hopefully it is), I kind of wish they'd just strip down the current Gen2, sort of a "Gen2.1":
Just give us the new fancy glass and tool-less zero and call it a day.
Skip the 36x (since most of us will still be shooting at 15-18x 99% of the time anyways), skip the illumination (since like most, I've only turned mine on to see if it still works now and then), cap the windage, and take away the lockable turrets (not needed).