Beware casting spoilers, if those bother you.
There’s a fairly thorough description of the video and a few more spoilerish news bits at this io9 article, but I’ll just leave you with what Lauredhel IMed to me when I sent her the link:
Dinosaurs! Angels! Mad-eye Moody!
Spoilery speculation is encouraged in the comments, so those who prefer to be unspoiled should probably not scroll down (but feel free to have a non-spoilery squee session on the open thread).