Harold Ramis confirmed all this brand new Ghostbusters 3 talk, and added a few other interesting nuggets of info. Check it out:
"yes, columbia is developing a script for GB3 with my year one writing partners, gene stupnitsky and lee eisenberg. judd apatow is co-producing year one and has made several other films for sony, so of course the studio is hoping to tap into some of the same acting talent. aykroyd, ivan reitman and i are consulting at this point, and according to dan, bill murray is willing to be involved on some level. he did record his dialogue for the new ghostbusters video game, as did danny and i, and ernie hudson. the concept is that the old ghostbusters would appear in the film in some mentor capacity. not much else to say at this point. everyone is confident a decent script can be written and i guess we'll take it from there."