First of all.... Did you hear Arceus' roar?! That is siiiiiiiiiiiiiiiiiiiiii *takes a breath* iiiiiiiiiiiiiiiiiiiiick! I really hope it stays that way.
As for the Plates, I totally agree. That has to be the case. Except... The plates in the title graphic are the exact shape as the golden plate on Arceus' head, and the green orb, well, is just an orb. It may turn out to be a plate or Type activator later, but I'm thinking it's just another item.
Can't wait to see all of Judgment! I noticed its mandala glows when it uses it...
What I don't like about the trailer is the opening, where they just copy and paste Dialga attacking Palkia from the opening of movie 10, then Giratina attacking Dialga from movie 11, right onto a blue sky backdrop. (Yes, the drawings used are the exact ones from those movies.) I know this won't show up in the film, but it was a cheap way to make a trailer longer.
Also, expect the backgrounds and everything else to be drastically improved by the time the film comes out - these are simply quick backgrounds. (We've seen them in movie 11, too - remember when Giratina was first revealed to be in the film, and Ash and Dawn both stood there as it got up and roared? Never saw that in the film, now did we? In it, they used a quick background to simply get the image out there. Also, the best example of this was when Shaymin was first revealed to be in the film. The scene where it does the sneeze in the opening originally had a backdrop of a flower garden - in the final cut of the film, it was changed to a dark forest.) I'm 99% certain most of the backgrounds seen in this trailer will either be entirely changed, or made to look better. They simply needed to get the trailer out there, so they rushed the backgrounds (or simply did not want to reveal the ones they're using in the film).
Saviour_Gundam: Giratina stays in its Altered Forme (the one seen in Diamond and Pearl) in the real world, not the Reverse World (which is its Origin Forme, as seen on the box art for Platinum). The clip from the opening showing its Origin forme is simply a way to drag out the trailer, and is directly taken from the 11th film and put on a different background.