Oh, I think they're already extremely interesting/instructive. Consider Border Collies; they can memorize <300 commands, which is pretty impressive. There aren't any grammar-producing results or indication of genuine understanding, but just the memorization points to a pretty good memory. And the border colly breed only goes back 1 or 2 centuries before it disappears in the general sheepherding/working-dog haze.

What could your 100 years of rigorous breeding do? I dunno; intuitively I feel that if silver foxes could be completely domesticated in a few decades, 10 decades ought to get border collies up to chimp-level cognition.