Why wouldnt he play CL? He did last season, getting 4 spot isnt that hard. And might I add, they won Europa League (plus super euro cup against Inter).
But yeah the contract thing is for higher salary then for wanting to stay in Atletico alone, he still can be sold, because he is the kind of player who leaves only for big big sum, and for that how long he has left in his contract wouldnt matter as much, because he would only be sold for sums atletico cant say no to.