I would hate to sell Kev, but if the money is right and he's open to the move... football is a business at the end of the day I suppose.
By all accounts Kev has already said that he's considering Saudi so I wouldn't be shocked if something is in the works. Tough to say.
Also, I think Pep signing an extension, even if only adding an extra year, would help give us some pull with Musiala. Knowing that your manager isn't going to be out the door after a season is a pretty big deal for these players (I'd assume).