I can not see us buying new midfielder in January so he should stay for squad depth but for the next season I do not see place for him and he should go on loan. For young player most important thing is to play regularly and this will not happen for Billy in Chelsea anytime soon.
Assuming we buy Rice he will play as number 6 and we have Kante who is amazing now!
For number 8 Kai, Mount and Kova are all ahead of him. That 6th midfielder spot should be given to Gallagher next season. Mount, Abraham, James, Tomori all got their chance in Chelsea after good Championship season and Conor also had amazing season there but he is also having great season in the PL season so it would be double standard if he is not here next season. And he is so ready! Also do we see Billy playing as number 8? I can see him only deeper.
Like I said, most important thing for young player is to play regularly and Billy needs this somewhere else probably for 2 season like other boys had. Imo game time they had in careers is the only thing that puts Mount, Tammy, James in better position now and ahead of CHO.
Every young player found their spot in Chelsea through loans and CHO is unique and this is why it is more difficult for him but I think he is gonna make it. Billy should not take that road.