Well from what I conclude Kishimoto is actually done since you have to finish the chapters weeks in advance, and we also heard from one of his assistants on twitter that they just finished making those 39 pages the other day.
Kishimoto has been technically done for some weeks now. I bet he's using that free time to make the animators cry once again with his demands for the movie.
Yeah, the releases for most of these series- if not all of them- have been prepared in advance, it seems. I think Mashima is about 5 weeks ahead of the publication schedule of "Fairy Tail," given his tweets teasing future chapters and when those chapters are acutally released.
Considering that it takes quite a while to produce a movie- And I think it's more difficult to make an animated feature.- as well as when the movie was allegedly announced and the finale of the series was teased with RtN, I think it's safe to say that things were planned very well in advance, which is kind of scary to contemplate, actually. On top of that, even the first opening of the first series has this nostalgic air, which seems to tease that a lot of stuff will happen. XD But then again, storytellers need to have many things planned out, so I guess it's no shock.
At the very least, I think that the movie is in post-production- Do they have that stage for animated films?- if it already isn't ready for distribution. In terms of the manga, I'm guessing only revisions, if they have that stage at this point, are taking place, if anything else has to be done.