The thing about labs is that there are so many poor quality "purebreds" out there that a person picking up a lab puppy can end up with a 50-100 pound dog at 19-27 inches with god knows what type of personality. Yours looks surprisingly like a show quality dog except for that tail. He could tip the scales at over 100 pounds when fully grown. My neighbors have a yellow that is 110 pounds at two years old. He is the height of a great dane. We call him their horse. Yours looks a lot like this dog as a puppy. I can't answer your questions about size because of the problem of overbreeding, but you could be in for a big, big dog.