I'd seriously consider selling if Bayern are still willing to fork out £100m+
1.) He'll have little impact on our season given he's going to be out until March and will take time after that to get back up to speed.
2.) He'll be entering the final year of his contract next summer and we'd sell him anyway at that point if he isn't renewing. We can at least get more value whilst he has two years remaining.
3.) Whilst players can and generally do recover following knee ligament injuries, it isn't always a guarantee and can cause reoccurring issues throughout his career. Especially for a player that relies on speed/physicality like Leroy. See Mendy as an example.
4.) No transfer ban for 2020, meaning there isn't the concern of being caught short should we need to purchase anyone. Sancho is a realistic replacement and we can reinvest the money gained from Sane.
It's a shit situation all round and I'd obviously love to keep Leroy, but if he still isn't looking like he's going to renew and Bayern are still interested, it makes more sense than it did before in my eyes.