A very good friend of mine had two separate severe tbi's, and she is now a fully functioning, athletic yoga instructor/office manager, with two kids and a very full, rewarding life. I don't know that she would say she's 100 percent better--I'll have to ask her--but if not, I'd still say that she's functioning better than a lot of people who haven't had tbi's. It is possible, and I believe that I will get better with more time and therapy.
I have totally recovered my cognitive function and my horrible headaches are gone (knock on wood!), so now I am just struggling with eye-related dizziness and photosensitivity. I'm going to a neuro-optometrist for therapy, so I am very hopeful it will help me recover fully.
If you think about it, I bet there aren't a ton of people on this forum who've completely recovered because they've completely recovered. A site like this is for people who are actively struggling and need support.