"(This is also the number one reason it gets bashed by the dickheads at Uboachan, but that's another story...)"
Pardon me, but I'm one of the dickheads at Uboachan, and I don't see anyone complaining about having new things to do in updates. If you really have seen people do that, then yeah that is a really shitty thing to do.
More on topic, my guess is that the creators will move onto other projects. A lot of them are developers of their own games (zenmaigahara, koronba, etc.), and once 2kki's done they'll probably have more time to work on said fangames. I don't think they'll abandon the 2kki project entirely, though, but I also don't know what they're going to do with it. We'll just have to wait and see.