If Liverpool loses to Salah and Mane together, their attack will be completely broken. Although Liverpool is a stable team, but still they rely heavily on these two players. So I don't think they will decide to sell these two players together. Despite the decision to sell Sadio Mane, Salah will probably be seen in Liverpool's jersey for a few more seasons.
Mane and Salah have been Liverpool's two main players in recent seasons, it is clear Liverpool will lose a lot of strength in attack if both leave together in one season. Salah and Mane have stabilized Liverpool's attack during this time, and if both of them are no longer in Liverpool uniforms then I believe Liverpool's attack will be a bit chaotic and not as good as the last few seasons.
I also believe that Salah will not be following in Mane's footsteps any time soon because Liverpool still really want this player to stay for the next few seasons. So whatever it is, Liverpool must be able to convince Salah not to go anywhere even though sooner or later he will be replaced.