Id believe Koukis going to finish writing it at least. That leaves character art, expression sets, CGs, programming a whole piece of software for a series that was always liberal with the use of silly little movement tricks to add flavor to a scene, advertising/marketing efforts so the game doesnt flop, etc.
Girls Garden having moderate success might be the games salvation tbh, because it shows that the IP can still make money, but convincing a publisher that visual novels as a whole can still make enough money to justify the initial investment risk is the hard part. The economy isnt exactly kind to doujin circles trying to make a game at the moment. *Floats off into delusionland about Fault ms2b*