If you knew him before? Then probably he's going to be very different.
If you've only met him afterward? Then he'll be the same man you've always known.
Life changes people. Usually. My cousin is low functioning autistic. He's the exact same 2yo boy he's always been. Even though he's now 40. Consider PTSD like any other life long, life altering event. Like becoming a parent. (Or moving out of their parents, or becoming a paraplegic, or, or, or.) People change. They struggle with new roles. They adapt. They grow. They find their stride. How long that takes, and how much it changes someone? Depends on a lot of factors.
Will 'parts' always be missing? Depends on how you look at it. If you want him the way he was pre-PTSD? Ain't gonna happen. Just like he'll never be 5 years old again. He's a whole person. Whether it's PTSD or a wheel chair or being a Daddy... People change. Sometimes for the better, sometimes for worse, more often both.