Hmm ... considering the other unique endings, that's not a bad idea. Unfortunately, it'll have to be head-cannon, since Drifty didn't do that.
To be fair, the two unique Chris endings (pretty sure there's only two) work because the circumstances keep the two friends near each other long enough for the event to happen (They both move to LA for the Lexi/Holly ending and they're just separating at the end of the Kira/Robin ending).
A reunion of the "high school club" could really have only happened right after the concert, and since all the epilogues happen probably 8-12 months after the concert, it doesn't really work. It could only work if one pair traveled to meet the others for the epilogue, which kinda goes against the overall message of the end-game -- that all things come to an end, to be replaced with a new beginning.
(It could have happened after the Paris trip I suppose, but that would just turn the epilogue into a Return of the King clone)
That said, there's no doubt in my mind that, over the years, the two couples would continue to meet for birthdays, holidays, reunions, etc. Just like I think all nine (unless you're an ass) of the "cast" would continue their friendships regardless of who the MC chooses. They had an amazing/heart-wrenching/friendship-bonding summer, and I think it's safe to say those bonds will remain strong the rest of their lives.
At least, that's how I choose to see it.