I don't really like endings for any show, but from the sound of it, this one sounds pretty interesting.
I'm mainly interesting in their Pokemon and the others that will be apart of this. Looking at the images, perhaps "Their Pokemon" means every one they have, so we'll see all of Iris, Cilan's, and Ash's Pokemon(The ones in Unova) which would be nice, Iris has all of her Pokemon out in the picture.
I can see Juniper, Fennel, Bianca, Luke, Kenyan, Trip, Burgundy, Langley, Jessie, James, and Meowth be apart of this in some way. Perhaps the gyms leaders that we have seen so far as well. I can see Trip feeling uncomfortable in the scene, maybe Langley would be uncomfortable too.
I doubt I'll like the song, but the scenes sound like they'll be awesome.