I am going to say that he is going to be a relatively big dog. Say, maybe 45-50 lbs or more. He looks like a Bull Mastiff Mix at about 7-8 weeks. His bone structure looks fairly large which would imply that he is going to grow quite a bit. But you never know with mixes. If you do keep him a while (say maybe 2-3 weeks), you might want to check his weight peridically. A gain of 7-10 lbs in a week would be a very "big" sign!