In the end of the day we both agree he wants to be important to the team. And exactly playing time / feeling valued, may be the reason he wants leave, which was my original suggestion for a likely reason to leave. Having two young must-starters in Frenkie and Arthur, a decent playing club-legend in Sergio, maybe 1-2 talents in Puig and Alena, maybe another starting-materiale transferred CM, and Roberto who at very least will be a 4/5th pick in midfield... And you dont consider that to be a likely obstacle for playing time next season? Not to talk about his decline and we dont even know who will be the coach next year.
Regarding decline. Last season he was a beast first couple of months or so, and for various reasons declined a lot and didn't stand out anymore but yet another player in the group. What he brings to the team: workrate and hunger he can only maintain for 45 minutes. Or else he wont actually contribute but just take a spot on high wages. Valverde has probably realized that, and thats the reason he hasn't fielded him more than those silly 180min and his big game vs inter wont change that much imo. Me stating "clearly visible decline this season" was a mistake, because he hasn't played enough to make that claim, but his work rate and hunger has for now seemed lesser than last season imo.
And, just because he has something to bring to the team doesn't guarantee him playing time, Sergio, roberto, New CM also have qualities who may get them picked in stead of Vidal. The midfield-constellation is still pretty new and is yet unknown how will connect best with who in what situations. In other words how much playing time will he get and how much do those 'qualities' of his really bring... We dont know that for sure. But we do know that midfielded is crowded, roberto, Sergio, frenkie, Arthur all are ubtouchable in this team and demand a certain amount of playing time while Vidal is the odd one out.
So I think it's fair to assume playing time may be a not that unlikely reason for him going next summer.
He wants a champions leauge, yes, but not on a free ride and I don't see Bayern or Juventus as possibilities neither, but maybe he will go to Arsenal to play in PL for first time, which would fit very well imo, or he wants to play for a big team like Napoli or inter in stead of getting spare minutes for us and just covering a spot for no real reason.