~~
Certainly Bayern Munich will not want to lose Musiala, they are not like Dortmund who are a profit oriented club. Bayern Munich will always want to continue winning the league title so they need every good and fit player in the team to help boost the team’s performance this season. I’m unsure about Sane’s position in this team. He didn’t live up to the expectations at Bayern Munich, it is very likely that Bayern will may reduce his wages in the new contract. Knowing Sane’s history at Liverpool, I very much doubt he will take that deal.
I can even guarantee that Jamal Musiala is much more important than Harry Kane, last season before Kane, Jamal Musiala role managed to contribute 12 goals and 10 assists so it makes sense for Bayern Munich to keep him longer. If they don't act soon, there will be many clubs who intend to bring him in at any price. He is still young but his maturity level on the field is unquestionable.
You describe this as if Bayern Munich could take the initiative and decide what steps to take next. But that is not how this works. Musiala is the one who decides how these negotiations will go. It didn't go unnoticed that the best clubs in the world area already after him. He can play this season without any pressure whatsoever and while Bayern Munich would like him to sign a new contract tomorrow, there is no good reason for him to do that unless Bayern Munich offers him a package that he can't resist. But Musiala knows that he is in good shape and if he stays healthy for this season and he performs well, his market value will go through the roof even further.
If I were him, I would put all the negotiation rumors aside and concentrate on football. Bayern Munich is onto it, but there is nothing they can do to pressure him into signing anything too early.