Salah and Mane are definitely important figures in Liverpool, and if they probably leaves. I bet Liverpool performance will surely drop next season. Am quite sure the team won't want to lost two of their best players at a time, if Mane choose to depart from the club, the management will do anything within their capacity to ensure they retain Salah. However, after Bayern Munich lost their key player Lewandowski. They basically need an experienced player like Mane to replace him.
Sadio Mane and Salah are good pairs in the team, they understand each other and have a very good teamwork that is perfectly going on. But the team are mute to listen to the demands of the both players, Mane and Salah asking for an increase in their salary, that's not too much for the board to handle. For sure, Mane is leaving Liverpool to face a new challenge while Salah might still be in the team because definitely, Liverpool board will increase his salary while Mane mind is already made up and he is ready to leave the team.
Mane's decision is unanimous now and indeed he will definitely go and change jersey with a new club next season.
Actually this is still a heavy blow in my opinion considering that in this case even though Liverpool players are very good from every line, losing Mane will clearly have a big impact there.
For Salah they should also make good things about him because if he doesn't want to be here too then it will be very difficult for them to make it through next season.