Its hard to say at this age wether he'll continue to be downhill, or if its because his butt is growing. I don't like how his neck comes out of his shoulders, he's almost a bit ewe necked. See how his neck drops a little in front of his withers?I think he's adorable, has a nice head, but my mare is a downhill, slightly ewe necked and I have alot of problems with her because of it. It makes everything just a little harder.
This horse, has an amazing neck. Its so uphill and light. We have foals from this guy and they're incredible to work with because everything is easy. (assuming everything else is right) http://vintageiberia.com/photos/lavtrot.jpg
I can't post the pic because its protected. But this is to get you an idea of a wonderful neck.
Also, his hind legs are really really straight. That makes for a flat trot, but that is also what you would be looking for in paints! :)
I'd say keep looking. I know he's a baby, but there are confirmation flaws I see that will stick with him.