Given the success rate Liverpool is currently experiencing, I don't think mo Salah would want to leave a club that is currently at the peak of winning the premier League and other promising European competitions for another club, same thing goes to Liverpool as I don't think they are not going to give mo Salah an extension of contract especially with the way he has performed this season, he has been able to score over 15 goals for Liverpool just this season and is highly likely to score more before the end of the season. In any case if Liverpool ever decide to let go of him, then it should be because of age factor which for me is not really an issue, at best they should extend his contract for two seasons instead of letting him go outrightly.
Mo Salah is currently enjoying the moment as the team is sitting in a well balanced position this season. Although he has only scored to goals in the UEFA Champions League, he has however scored 15 goals in the Premier League this season. Liverpool is currently leading both the Champions League and the Premier League but has see a well circulated player performance in terms of distribution of efforts among the players. No player is considered outstanding and none is considered lower. The chemistry between the team players have been well circulated among the team bringing about efficiency across all ends.
I've checked the last 5 games played by the Liverpool team in the Champions league and none of those matches were lost by the club. From there challenge against Bologna which produced 2 goals win to none to their away game over Leipzig which produced a goal win, to their game against Leverkusen which produced 4 goals win to zero then their challenge against Real Madrid which produced 2 goals win to none and the last match fixture against Girona still securing Liverpool with a goal win over the opponent.