For the awareness of the elderly, 6-7 is starting to evolve, at least locally, into a call and response with the response to a 6-7 hand gesture being 8-9 with a kind of horizontal movement of vertical hands in a similar fashion. I'm unsure how local the trend is, it's true origin, or if it will spread.

It's interesting that to those not initiated into the call and response by peers will see knowledgeable non-peers providing the response as mocking or failing to understand the meme, thus further cementing it's role as a tool as an in joke to the 6-7'er, despite them now being on the outside of the evolution of the joke, which is a wonderful contradiction.