This won't come as any shock. "Ghostbusters" actor Ernie Hudson -- who played Winston Zeddemore, the late enlister with the Ghostbusters in the 1984 original film -- says Bill Murray is the hold up for the still-gestating "Ghostbusters 3" picture. Anybody coulda really told you that. All the four Ghostbusters have script approval -- the real "four" being Murray, director Ivan Reitman, Dan Aykroyd and Harold Ramis -- and they have to all be on the same page for the movie to move forward.
Of course, everyone seems to be pretty fine about the concept and idea of a third "Ghostbusters" film except for Murray who has been notoriously critical and outspokenly negative about the project in the last year or more. In a recent interview with MikeMovie (via DreadCentral), Hudson explained the issues, describing it as an mix of Murray being picky and passionate. And it's been unclear up until this point if Hudson would appear in the film or not (Sigourney Weaver will be, Rick Moranis might be), but from the sounds of it, it seems he's on board as well.
Dan and Harold are working on the script. If it happens we will see but Bill has been the hold up. His definition of good is a little bit different than everybody elses. So we will see, I would love to see it happen. I know the fans have been asking for it ... so hopefully. Bill's a great guy, he's kind of quirky but I love him. He's a guy who is very much into what he's feeling. I know he really cares about his work, which is probably why there hasn't been another Ghostbusters as of yet."
So yeah, as you pretty much figured. Last we heard "Ghostbusters 3" might shoot in the spring of 2011 and Aykroyd recently confirmed that actors who are "strong possibilities" to take up the new mantle include Bill Hader, Anna Faris and Eliza Dushku (Will Forte has been rumored too).