I can't see how the current standoff will transition to the point where Messi actually leaves Barca. I know it's possible, but I'm just unable to imagine what the moment is when everything just clicks.
1. If Messi could actually leave on a free, he would've left by now.
2. If Messi could leave on free, but wanted City to compensate Barca for old times' sake, he could still hop on a plane and Barca would've no other option than to quit the bluffing game and accept whatever fee they get.
Since neither of the above two things have happened, it seems to me that it's not as straightforward as imagined and both sides stand to lose something.
Maybe Messi knows that the contract is not as clear cut as made out. Barca will probably sue him if he leaves the club and maybe he feels that there's a chance, however low that Barca wins. Too much risk. Or maybe he doesn't want to kill whatever goodwill he has left at the club by dragging this shitshow into a court. I think a lot of hate people Barto and support Messi right now, but if this thing gets to a court, maybe there's a fear that he ends up on the losing side of history. At the end of the day, as much as people love Messi, Barca supporters/staff/players love the club more.
And if that truly is the case, then I don't know what he can do to force the club to sell him. Because right now, to me it seems that Barto knows that he's finished anyway so he would rather drag Messi down with him than concede defeat. His tenure is over next year. He'll sell half the players, settle the debts, the club will go to shit, but at least he won't be facing any financial penalties and most importantly, he will have had his little victory by forcing Messi to spend another year at a club where he is doomed to not win anything.
To me, this isn't a matter of intention because it's clear that Messi really does want to leave. This is about how far either side is willing to go, how much are they willing to risk. Barto can't lose because he has nothing left to lose. Messi has everything to lose.