Bill Murray will not be involved in the long-gestating Ghostbusters 3 project according to writer/producer/star Dan Ackroyd, who told the U.K.’s site that "It’s sad, but we are passing it on to a new generation."  In spite of the fact that old Ghostbusters gang won’t be reuniting on screen, Ackroyd believes that Ghostbusters 3 can be a success without Murray, and that he’s "confident we’ll be in production in the next year."
Ackroyd confidence is based on that fact that "now we’ve got a studio on our side."  He noted, "We’ve got a brilliant new writer on it, and we’ll be passing the torch on to a new generation."  He acknowledged that previous attempts to get Ghostbusters 3 going were marred by "concepts that weren’t right," but he feels that "now we’ve got a good structure and will make it happen."
Earlier this year Ackroyd noted that Murray, whose interests increasingly appear to be limited to quirky independent films like Wes Anderson’s Moonrise Kingdom, was unwilling to participate in a third Ghostbusters film, which he then stated was “in a state of suspended animation” (see "Bill Murray Will Not Do the Movie"), but it is clear that there has been considerable movement toward a very different version of Ghostbusters 3.  
Of course there is no guarantee that the new Ghostbusters 3: The Next Generation will get made, but at least it does appear that the project is showing signs that it may yet emerge from cinematic limbo.