The more I think about it, the more I think he will end up staying. The club have the power in this situation and I don't see anyone making an offer that would tempt us to sell. Their isn't much in terms of strikers available this summer, so it's not like we're keen to offload him to free up the budget for someone else. And being out of the CL hinders the possibility of bringing in a top player if they were available anyway. Ronaldo is on huge wages and there may be clubs willing to pay those, but it would still rely on us accepting a minimal or even free transfer fee which we don't need or want to do. Are clubs really going to chuck £20m plus our way plus his wages at his age? Doubt it. Makes more sense for us to keep him if he could be the difference between CL qualification or not, and look to replace him next summer when we have a CL budget and CL football to tempt potential signings. A younger player can waste a year moping around to force a move but Ronaldo can't at his age. He has limited time left and will have no choice but to accept he's staying and give his all.
Only question mark is whether he can fit into ETHs style and if he is positive or negative for squad harmony. I think he can fit into ETH's team and that I it'd be best for him and us if he is used a bit more sparingly. Get him on the pitch for 60-90 minutes a week rather than 180, and he has less need to reserve his energy. He still offers more of a threat in the box than the rest of our forwards combined, his link up and hold up play is underrated, with the ball at his feet he is quality, and he is still fit and can work hard in spurts. Again, takes strong management to make those calls but Ronaldo has no option but to accept it. He can't sulk his way out, he can't refuse to play, and no club will pay both him and us enough to let him go.