Mane in Lego to the Saudi Pro league and Kane to be recruited as a substitute is the scenario that is being carried out by Bayern Munchen so far, the realization of a fast move gives Kane plenty of time to adapt.
The last news that i have heard about a possible transfer of Sadio Mane to al-nassr was that Bayern would let Mane go for a transfer fee of around 30 Million €. If those numbers are true, then this obviously is not even a third of the amount that Tottenham is asking for Kane probably a fourth with bonuses included. I am pretty sure that there will be official confirmation about a transfer of Mane to Saudi Arabia pretty soon but i doubt that this will have any influence on the situation with Kane.
Yes, what happens if Mane really leaves but Bayern Munich fails to bring Kane, will it be a blunder too later. Because I think, Kane's move is still very doubtful because anyway, Tottenham also seems like they will never be willing to let Kane go. But yes, if Bayern Munich can propose the payment Tottenham wants, then it is likely that Kane will leave too. Because after all, Kane has wanted to leave for a very long time, and maybe at this moment Kane's desire to leave can come true.