VERY nice looking pup. Great face and great posture. He looks perfect in terms of how he is carrying the weight. My guy is a week shy of 5 months. He is in his mid 50's lbs. I think at this stage, it is hard to project, but as someone mentioned, your best barometer is the sire and dam and how big they are as adults. From 3-6 months, they seem to gain weight at a steady calculated pace and then it will slow, stop and start. My guy was good for 3lbs a week and still is, but I expect that to slow. Their body's also begin to take on that GSD stance and they get leaner to the eye. Everyone I know (experienced dog people) look at my guys paws and proclaim he is going to be over 100 lbs. I am not so sure and I am not counting on it, nor do I want him to be over 100lbs. He might, but his dad is 85lbs and his mom is in the 70's, so it's hard to imagine he will be 20 lbs heavier than his Dad. People always focus on the paws, I wonder how much truth there is to it?
Here is a recent picture, you can kind of tell how big his mitts are.