As a yearling it is hard to twll :)..he stil has some growing to do. Right now, at least in these pics, he is built "downhill" in that his croup is higher than his withers. A good dressage horse has an uphill build which helos to stay light in the forehand and engage from behind. He has a nice angle to his shoulder and his legs look straight though he may slightly sickle hocked, or, it could just be the way he is standing. The better leg conformation is to be able to take an imaginary line from the point of the buttock and be able to drop it straight down along the lower cannon. While this might make the thrust from behind a little easier, the stress of dressage could end up causing stress on the bag legs and eventual lameness issues. Again, this could just be the way he is standing.
He has a nice short back, good heart girth and from what I can see a nice neck and probably nice wide throatlatch area.
I would say that athletically he probably has some potential but again, how he grows may affect that...just have to wait and see.
He is a beautiful boy; I am especially partial to Dark Bays..He has a nice face and kind eye..looks like he can be mischevious though :)