It depends what you mean by 'replace'. There are very few players of his calibre, and the chances of Liverpool being able to obtain any such player and have him fit into their team and deliver in a manner comparable to Salah, well that seems pretty unlikely and the experiences of many clubs tell us that it's rare, regardless of the big budget they may boast if he leaves in the summer.
He's the kind of player whose contributions are perhaps more effectively replaced by reshaping the team's attacking system. I believe that Klopp is certainly capable of restructuring his team to ensure that Salah's goals come from others, but given the pretty underwhelming returns of Liverpool's newer attackers so far, I expect that there'll be an immediate trough before he's able to find the formula and system that endures.