He will be allowed to leave on a free transfer, but finding a club that wants him and is willing to cover his wages will be really difficult.
I'd say that the chance of him leaving in the winter window is less than 50%.
Honestly, I do not think Cristiano Ronaldo should continue to be a part of the Manchester United team anymore. Because that is going to be a disaster for his career which it already is in my opinion. It is true that any other team is not willing to give the type of salary which is being given right now to Cristiano Ronaldo. At the same time, it is also true that Manchester United is not even a suitable place for Cristiano Ronaldo anymore. I think Cristiano Ronaldo will need to at least take a 40-50 percent pay cut to get a decent team.
I have to disagree that the chance of Cristiano Ronaldo leaving Manchester United in this transfer window is only 50%. I think it is almost close to certain that he is going to leave Manchester United.
Best
Duke