Pokemaniac
Member
Are most the previews really that ambiguous? The only one I remember being completely different was the Zoroark movie where Ho-Oh and Lugia were shown instead. There was Regigigas for the Giratina movie, but it technically showed up there.
I do agree that Zygarde has a good chance of not having a prominent role in the movie and Volcanion will be the main focus. I definitely think Gen VI is getting another game next year but I'm not sure about a Gen VII Pokemon as the only reason why Lucario got its own movie so early is because Gen IV was supposed to release in 2005. We'll likely get news on it by December anyway.
Perhaps calling them completely irrelevant was a bit harsh. What I'm getting at is that these things are usually made before any work on the movie is completed, so you can't really use them to predict what the movie itself will be about. As an interesting historical note, the first trailer for the very first movie ended up being somewhat non-indicative as well, since the first move was originally planned as the ending for the anime.
Also, I didn't mention it above since it wasn't really the focus, but a Munchlax actually got significant screentime in the 7th movie. It's kinda crazy when you realize that 3 of the 4 Gen III movies had a Gen IV Pokemon in them.