It's never coming out because it's GZA's Home Movies, not a real documentary.
If Wu-Tang wants a documentary, they should hire a documentary filmmaker.
Because: 1) they don't know how to make documentaries and 2) if a rap group makes a documentary about themselves, it's just going to be a rose-colored press release. Their main priority won't be telling a good story. It'll be looking cool. Gotta cut that scene, I don't look cool. Oh, keep that soundbyte in, I look cool.