If the new stuff is very compatible with both old versions and different 'builds' (heh) of 5e, then there's a way to create shared experience.
"Man, our group finally finished that new 5e adventure, 'Terrible Temple of the Devil-Crocodile' last night. It was crazy."
"Oh, I love that adventure. You guys are running just basic core, right?"
"Yep, that's right. The room with the six-headed snake almost TPK'd us."
"Dude, us too. We're playing using the grid-tactics add-on, though. Some killer set-piece encounters in that module."
"Sweet. Did you guys rescue the disguised hag in the cave?"
"Hahaha - hell no, we stabbed the shit out of her."
"So did we!"
The supplemental stuff is just stickers and spoilers. It's the chassis that matters.