This is actually taken from an old teaser shown on Japanese TV during the airing of Pokemon Diamond & Pearl 1 hour special (Episode 13 & 14).
The two screenshots were taken from the teaser, featuring the battle between Dialga and Palkia, possibly in their own dimension before the two Legendaries mysteriously appeared in Álamos Town.
Dialga and Palkia prepares to battle each other. Both symbol of diamond and pearl can be seen glowing and illuminating the two Pokemon as they charge up their energy:
If you haven’t watched the latest trailer for the 10th Pokemon movie, here it is:
You can see the part when Darkrai first made its appearance in the movie, protecting Ash/Satoshi and Alice from a blast from either Dialga or Palkia. You just gotta love how Darkrai’s name was said at the end of the trailer
The director for this movie, Kunihiko Yuyama (????) had mentioned before that Darkrai holds the key to this movie but would not elaborate on which side it is on. But based on the trailer, we could probably speculate that Darkrai is indeed trying to stop the battle between the other two Legendaries.