Well, at this point it would be great for Barcelona if he leaves, and in a sudden way.
I think it's the only way to clean Barcelona from their people in charge (Bartomeu and staff). These pleople are killing the club.
It would be a sad but necessary sacrifice. And make him even a bigger legend. Of course some people would see it like "he leaves now that the team is not strong.." But the leaders of the club are ruining it, and if you give your heart and maybe win trophies, they would get the credit. And that sucks.
Thinking about it, I don't see him going to Pep that much. Against what everyone sees here, I think the relationship between Mourinho and Messi is not bad at all. And it became clearer after Jose left Madrid. Mourinho had a meltal war with Messi, but it was clearly a tactic trying to keep him out of the game somehow. I think they could perfectly work together. United has not only the money but the sponsorship of Adidas, which is important.
Don't think the relationship between Messi and Guardiola finished that well.