If Liverpool wins the league this season, then sending Salah away for free could be considered terrible by the fans, hence it is going to be some issue without a doubt. I understand that we are looking at Salah getting older, but that doesn't mean that Liverpool has a chance to not sign him, whatever Salah wants, they are forced to accept.
Because if Salah leaves and they do worse, which they probably will, then every fan will be incredibly mad with the ownership for sending salah away. So Salah has all the power to strong arm the team into getting a good contract, he can do whatever, and to be fair looking at how he got paid, he hasn't been paid that much money for most of his time there, just recently he has been paid fine, but early on he was paid very low.
Liverpool management must make a very wise decision, even though in the end Salah will also leave the club like other legendary players. Most likely Liverpool will retain Salah, even though they have to meet his high salary demands. I think this is understandable, because it is in accordance with his contribution on the field. Liverpool will never be ready to lose Salah, only a few players are able to make a difference in every match, and it is difficult to find a replacement that is equal to him.
Liverpool fans will of course encourage the club to retain Salah, even though he is no longer young. Moreover, if at the end of the season Liverpool is able to win prestigious trophies such as the Premier League or Champions League, it is certain that Salah will get a short-term contract from management. There is a lot of speculation regarding Salah at this time, the Saudi Pro League club is also reportedly interested in recruiting him at a fantastic price.