Following the merger of Vivendi and Activision, Sierra is now a subsidiary of Activision Blizzard, who is now said to be streamlining Vivendi's portfolio of games, which includes the Ghostbusters videogame.
Activision Blizzard has stepped forward to deny that the game has been cancelled, whilst Sony Pictures, who owns the rights to the movie, told Variety that it is working with the publisher "to evaluate various options surrounding the release of the 'Ghostbusters' video game."
Furthermore, Variety believe that Sony Pictures is now talking to other publishers about picking up the title and plan to release it "to potentially coincide with the 25th anniversary of the original film in '09."
Ghostbusters as a brand is huge and the game has already received plenty of exposure, which should mean they'll be a long line of publishers queuing at the door. It now seems that whoever has the most cash, or whoever is willing to spend the most cash, will emerge victorious.

At least we can be safe in the knowledge that Ghostbusters is still going ahead and with increased development time it may even be a decent game.
Source :: Ghostbusters