Well, as usual, I have a long, illogical, and outstanding theory, so lets get it done with:
Teh next film in Japan will be abotu Shaymain and giritina, as indicated in the title. I am assuming this will be out by Autmn or next sprnig at the latest. A couple of days befroe the release, just like with darkrai, pokemon will put up a page for Shayamin on the website, and we will have an official release. THen, hey will make a set with Shaymin, I'm betting two sets time. (this set, one more, one more, and then shayamin) arceus is more tricky, because the movie won't be out for naother year and a half, possibly two years, and we will be in for a long wait, so hold on tight. Why so long? BEcause it will be the most extremely amazing megeganza eye tearing bum gluing to seats kind of pokemon movie ever. Arceus will be officially revealed, but it is more tricky this time. The movie will reveal alot about arceus, and this will all happen before arceus is obtainable in the games. SO first we will have our movie, then we will know everythign abotu arceus and get really bored of him, then we will have the arceus event. But what about the TCG? SInce the TCG concised the elements down to 9 types (fire, water, grass, l;ighting, psychic, fighting, normal, dark and metal) we will have one for each type, each card having the same move but different powers depending on its type. And of course, Arceus lvX.
But now we have the threorising bit of my theory.
Sad part is, I am late for schol so stay tuned and you will find out tonight!