They tried an upgrade before and it had problems. Personally I feel things are fine the way it is. The site has been condensed quite a bit already, and the only thing I could ask for is an auto-save draft of a post and tagging abilities.
Might as well just switch to Xenforo then. I know that was a consideration of a platform switch by the owners...but whether that will even happen is another question entirely.
Maybe just run a report on anyone over 500 or 1000 posts and give them a special tag or title on the new platform. One like Veteran - which allows people to recognize their commitment.