The good thing with Guillain Barre is that almost everybody recovers within a year - something like 80% full recovery, another 10% with a few residual difficulties with weakness in the feet primarily, with a few not getting much back. He’s got a year or so of rehab ahead of him though, carefully walking the line not to overdo it, as that can cause relapse.
My brother-in-law did not recover. He lost all ability to move, breathe on his own, talk, eat, etc. and eventually died.