Truth be told, Bill Murray really made Ghostbusters. Though it was certainly an ensemble film, it really is in a lot of ways his vehicle with him as the main headliner.
Murray has stated though that he's against appearing in sequels and I actually respect that a lot. I know he's been trying to take his career and the type of roles he plays in different directions and I can understand him not wanting to revisit the past.
It would really be a shame to not have him involved in some way with a future GB film, but the truth is these guys are all getting really, really old!
As much as I loved the classic team, I think it's time to move on to some new 'Busters. Maybe having the old team training new ones or setting up new franchises around the city. I know a lot of people are against such an idea but Venkman, Stanz, Spengler and Zeddmore are going to have to be chasing ghosts wheel chairs and walkers soon. LoL