My prediction:
He admits to having a "Parkinson's-like condition" (there is a whole slew of "Parkinson's-like disorders, and he has symptoms consistent with them) but not actual Parkinson's disease. This allows them to claim they did not "lie" when denying he has or has been treated for Parkinson's.
This will allow him to step-down to "focus on his health."
Honestly, if I were him, I'd do it NOW - and allow Kamala Harris the power of incumbent presidency to run in his place. He likely will want to finish out his first-term, however, so I think that is what will happen.
I believe this announcement will be made before the end of July.
Just putting it down in writing in case I'm right and I get to tell you knobs how smart I am going forward.