Ronaldo is not going anywhere for the time being. I think all he cares about is the money. Why else would he stay at United when he knew he wouldn't be a starting player again? He had the choice of clubs. United are not playing the Champions League this year, there were plenty of clubs he could go to and play CL. Shame to see a great player fade away. I think PSG has made quite an impression so far. In my eyes they are the favorites to win the title and not City.
There was chance for him in last transfer window, but sadly nothing positive happened for him, so he is staying here with now most chances he will try to stay here until end of his career because now positive development happening in Manchester United and their new system is also giving them good success with this all most chances they will be able to qualify for the next Champions League which is the biggest desire for Ronaldo and if current team done then he could be happy man even now his role is just for one half or around 30 to 40 minutes but still good because without any doubt now age factor is also having his impact on this legendary player.
About Champions League nothing is sure because right now many teams are doing average performance and few are doing amazing, so anything can change in coming matches specially as few players are already injured and out of competition for some weeks which is also going to have some problem for clubs.