It is just a feeling. But I believe if they do not bring in a really good coach, he is going to move out of the squad.
Obviously you are stating an absolute fact
In this situation when coach is going to be changed after the end of the season, most players will move out of the club especially when they know that alot of the other clubs out there wants to sign especially when they know their playstyle wont align with the new headcoach strategy.
but indeed if Ollie Watkins has decide to stayed at Aston Villa he will playing at Champion League
First of all, there are 3 other clubs that will play on UCL so what makes you think that his only options to play in UCL would be staying in Aston Villa? We all know City probably wont need him but Arsenal and Liverpool could be bidding for him. He got alot of potential and definitely going to be much better on another team