I think if we were going by Pep's demeanor alone and what he has been saying, I dare guess many of us would be sitting with a half expectation he would actually extend. In the recent months he has been positive and has hinted at possibly extending often. Even immediately after the final game, it was all left very open.
The 'expectation' that he will leave is very coming from outside noise and a few claiming to know the supposed 'feeling around the club'.
It is also coming from this rumour (if there is any truth to it whatsoever) that Txiki is retiring. And as such Ferran is supposedly moving on, and an assumption that Pep can't function without them. And then in turn that KDB and Ederson and others would follow him out the door.
But (if at all true to begin with), why Couldn't Pep continue without Txiki and/or Ferran?
He always starts his praise for his environment and the club with the Chairman. And extends it right down to the medical department and backroom staff. All that would still be in place, are we supposed to believe he is that fragile that he can't hack it without Txiki?
Yea it is a reasonable assumption that they are so close that they would want to all leave together. But it is also a pretty basic one and quite banal. They are not attached at the hip, they are adults. Pep didn't need them to go to New York, manage at Bayern, and chances are his next managerial job after us won't involve them anyway. Not convinced it is a rule he has to leave with them, if indeed either if them does leave.