he might beat gm in blitz or rapid but there is very low chances of him beating gm in classical chess
That's wrong. A 2300-something player has quite a few chances to beat a GM at classical chess.
What is unlikely is that he will achieve consistent results against GM opposition when he spends most of his time on his streaming stuff instead of working on his play- but then admittedly he gets paid much better from what he's doing now. I do not like most of his streaming stuff, but kids like it, and this is what matters.
Unless he focuses on his play, I do not see him having chances for GM. Heck, his rating is the same as mine when I was 58 y.o. which means that he is playing casually, already (he cannot be on the decline when he's still 28 y.o.)
Does he need regaine though?
It may be too late.