Bayern Munich are really after de Ligt currently but for now it seems like just an interest. I haven't heard of an official offer yet. Chelsea are in this race also and I see Bayern Munich one step ahead of them. But the opinion of the player is the most important point here of course. de Ligt can be an important part of the team if he stays at Juventus. Because Chiellini has left the team. If he doesn't desire a move out of Italy then Bayern Munich and Chelsea both might be unsuccessful about signing him. Unless they pay the release clause amount of course. 
But again - if the player wants to do it, he will do it, if not, he won't. I think such a strong player would fit into Bayern's squad, which is probably why they are one step ahead in this transfer. But will Juventus let him go if they can't find a replacement for him and already the departing Chiellini? Maybe yes, but then the game will be difficult, and they understand that
If they sell de Ligt for a huge sum of money like 90-100 million euros then I don't think they would have any problem on signing a replacement for him. There is nothing more than defenders in the transfer market and there are many skilled ones also. Let's say they couldn't sign any then their defense would be in a bigger threat. Because I believe they would definitely need a defender right beside Bonucci to have a solid defense. Chiellini's departure makes them become in need of a solid defender.