A couple of days ago, again Ghostbusters Director Jason Reitman shared a photo on Twitter of him, his father Ivan Reitman (who made the original Ghostbusters), and new stars Carrie Coon, Finn Wolfhard, and McKenna Grace, along with the title "The whole family is here." It's pretty simple and does not have any old Ghostbusters or ghosts, but Consequence of sound I discovered what seems to be a pretty obvious clue about Reitman's younger film: that child looks a lot like Egon Spengler.
The glbades! Hair, maybe! The … well, it's really just those two things, but that legend mentioned above can provide another clue. "The family is here" is most likely a reference to the appearance of the two Reitman and to the fact that the three actors are playing a family, but why should I do it? we, the community of Ghostbusters Fanatics, do you care about random families unless they are Spenglers? Consequence of sound says the film is about "a family moving back home to a small town where they learn more about who they are", and it seems that it would be an easy setup for the plot to say that Grandfather Egon died, leaving an old Ambulance in a barn and some kind of ghost mystery.
Or maybe it's just a visual wink meant to remind viewers of Harold Ramis. That's not so satisfying, but at least the rest of the original cast will show up in some capacity. Also, Paul Rudd will be there.