She did not say that she would not make a public release with 100% certainty. She said that it is a possibility, meaning she might still release the full game (but, like I said, I doubt it will be as good as it would've been if everyone continued to help her).
I really do not like this idea to be honest. You should've gotten her permission first (although that might be a little challenging given the current situation). Not to mention, the story will not be what it was intended to be. Seeing as how the storyline is apparently the strongest portion of the Dark Rising series, and with how passionate DRG seems to be about the story in her games, I think it would both end up insulting her, further encouraging her to not come back to this community, and end up with a feeling while playing the hack "Well, this is cool I guess, but I'm still not seeing the events of the game fold out in the way DRG envisioned them, so why care?" There is also no guarantee that this team you put together will have the dedication and work ethic to see the game to completion, not to mention the possibility of the content the new team comes up with having a chance to clash with the already created content. Finally, there is also the fact that the Dark Rising series is supposed to be a trilogy. How are you going to do the story and gameplay features for a game that DRG has probably not even given a single thought to, nor even started a thread for?
All pros and cons considered, this just seems like a bad idea to me. She could always come back, release the second game, then start over on the forums fresh with the third game. Maybe I'm foolish for thinking this, but I still want to hold out on the hope that she will eventually return.