Interesting fact: Pokemon have made movies of every event pokemon, plus it's in the order of the national pokedex! First manaphy, then darkrai, then shaymin now arceus!
That's actually a fairly well-known fact XD
Every movie involves one or more of the legendaries, and if they can shove an unobtainable legendary in somewhere - they do. Myself, I'm curious to see whether or not Ho-oh will
ever have a proper movie appearance (Mew's transformation doesn't count), and if the emotion trio/Creselia will be left solely to the Anime or make it into movie 13/14 somehow (stranger things have happened). Little chance Raikou will ever see a movie appearance due to the special, but you never know... Mew's been in two movies now, and if they did a G/S tribute it could easily involve Raikou and/or Ho-oh.
But... getting slightly off topic now XD
To put things back to movie 12, Arceus looks purdy in motion. The trailers released so far just make me more interested in this movie. Not too much longer now until it hits theaters... but by the time it's actually out in a way I'll be able to view it I'm sure most of my anticipation will have worn off like it did with movie 11, lol.