There's no way he'll be the "same ole Fitz." If he is, I think it's lazy writing.
I wouldn't believe him going through that near death, potential (probably) loss of motor skills (permanent or temporary with immense physical therapy), possible loss of brain function and the likely rejection of love from Simmons (strong feelings for him, just not THOSE feelings) and not coming out with a lot of issues.
He went through the grand slam of intense trauma: physical (loss of motor skills), mental (possible loss of brain function), emotional (likely rejection from the woman he loves) and spiritual (near death experience).
I think he can come back, still be the brainiac we know and love. But I don't think he will be that happy, bubbly, goofy, naive kid he was before. I think he'll be more like a combination of the Fitz we saw in a few episodes this season, including Beginning of the End, F.Z.Z.T and The Hub. He'll be more narcissistic, hardened and even a little resentful. But he can still have those moments of boyish charm, as rare as they'll be.
Does that make sense?