Well, the ones that are still alive and working. Harold Ramis died several years ago and Rick Moranis is more or less retired from showbiz. Will be interesting to see what comes out of this. I enjoyed the first two and the animated TV series The Real Ghostbusters back in the day. Haven't seen the recent reboot yet, though.
As far as I understood, Moranis left acting to raise his kids after their mother passed away. They must be grown up now. I hope they at least offer that icon a role.
I'm so looking forward to this! It was one of my favorite movies, growing up!
EDIT: Also, Sigourney is mesmerizing.