If Juve win the CL (unlikely, they always choke finals) it would be the perfect timing for Allegri to say goodbye.
Imagine something else - Monaco knocks out Juventus in the semi-finals. Would you still want Allegri under these circumstances? We lost in the Champions League because of our own players, manager and tactics, not because Allegri is some sort of a magician or genius. That doesn't mean I don't like him, he's done wonderful job, especially for someone who received so much hate when appointed as manager of the team.
Juventus played outstandingly well in defence and were clinical on the counters. It's nothing new in our history - Bayern also achieved it under Jupp Heynckes against us back in 2013. Whoever gets appointed as manager of Barcelona knows he has a lot of problems to deal with - player egos, contract terminations of half of the squad
and etc.