Apparently they gave info at the screening such as the budget was around $80 million and they are finished with it.
The OP thought it was a good movie but don't expect a comedy like the original. It's more like The Force Awakens "but better" because they go further with the concept.
Speculation seems to be right and Summerville is filled with Gozer worshipers.
One big twist we never thought of: Paul Rudd is a descendant of Shandor. Although he, as well as the audience, doesn't find out until act 3.
Shandor appears as a ghost played by JK Simmons.
All 3 OG busters suit up for the final battle. Gozer can teleport people now and teleports everyone to the firehouse HQ in NYC. Gozer transforms into an entity that resembles a terror dog. The firehouse gets destroyed. The movie ends with the OGs and the kids rebuilding the firehouse. Egon appears as a ghost and smiles at them. They get a call and they all go to on a job together and the movie ends. OP called it "beautiful"
Ghosts in the movie include: Slimer, 3 terror dogs, a ghost lady, ghost police car (the sheriffs car turns into it), ghost toilet, ghost baby staypufts (apparently in the barn), three Slimer like ghosts
There is a Gozer mini temple down in the mine.
The film opens with a de aged cgi Egon in summerville fighting the Gozer followers who want to bring him back. He stops them and then retires in the farmhouse but keeps the equipment to occasionally check. (OP said they don't know who played him, possibly Oliver Cooper aka "Elton"???)
He apparently dies of old age or a disease. The OG's don't bring it up.
Trevor and Celeste are pretty much friends but Phoebe falls for Logan Kims character.
Celeste is Winston's granddaughter.
Janine and Winston are married.
Callie is Egon's daughter - Trevor and Phoebe are Egon's grandkids (obviously...)
The suits are the 84 ones. The ecto 1 in the barn is the one from 84 that Egon rebuilt. Ray references the statue of liberty incident and acts apparently "senile" in the movie.
Paul Rudds full character name is Jason Shandor Grooberson.
Dana and Peter seem happy together. She doesn't do much except give some exposition.
This Post Contains Spoilers