I don't think Kim leaving would be that much of a problem for Bayern Munich. They already got De Ligt to play as a replacement for Kim right now. Let's get real, De Ligt is a very good defender. Bayern Munich does not have many serious matches before Kim returns anyway. Even if he does not return then that would not be much of a problem as I have said before. But the thing is De Ligt is probably linked with Arsenal right now, if he leaves then that would become a problem for Bayern Munich.
Isn't it upside down? Here Kim is the one who was just brought in last summer as a replacement for De Ligt and that's why we can see De Ligt spending his time as a bench warmer. So I don't think Kim will leave, especially since he's only been at Bayern Munich for half a season and he still has a lot of work to do to strengthen the defense. Thomas Tuchel preferred to pair Kim with Upamecano and I think that is what caused the relationship between Thomas Tuchel and De Ligt to crack.
It is true that De Ligt is linked with Arsenal but that doesn't guarantee whether he agrees or not, but if there are no other options and he wants to immediately increase his playing time as a player, then De Ligt must leave for a better future. Moreover, Arsenal is also a good team and they can always be relied on.