Looks like we're going to get a little lead in to the movie when it comes out in October next year! In a PDF released by Little, Brown and Company detailing releases for 2017 this little tidbit showed up. What sort of things will be revealed? I guess we'll have to wait till 2017 as the release date gets closer, but it looks like they are going all out for this movie.
Not only is this Prequel book coming out but a number of other books as well! I'm not sure which have been announced here already or not but the Prequel book seemed to be the biggest news. You'll have to dig through the PDF itself to find the info on the other books which seem to include some MLP stuff, some CMC related material as well as some EqG stuff too.
Thanks to Twilight Sparkle for letting us know!