here's proof it's gonna happen http://www.slashfilm.com/2007/02/03/ghostbusters-3-confirmed/ it maybe from feb but it's still this year bill murray wanted venkman dead and come back as a ghost to help out
I think the lack of any further development on a GB3 film since a bit of wishful thinking in February is a likely pointer that it won't happen, at least not in that format.
