Quoted from JodyG:
Stern hasn't officially sundowned GB yet. They usually post on FB when they are doing the last run of something. Metallica was a few months ago, and Star Trek was this week. I know there was a batch of GB pros going through in the last month or so, according to someone who went on a factory tour. If code does finally come, you can bet there will be a few new sales at least. So it would behoove Stern to keep that item number open for production until at least that time.
Ghostbusters is in the archived section of the games page on Sterns website. To me that means this game is no longer in production. Maybe they let it go quietly in order not to upset anyone that this game is old news to Stern.