Exactly, no way would City be willing to offer an extended contract with increased salary on any player who has such an injury with both an uncertain recovery time and uncertain outcome. Bayern will be even more cautious and I suspect would want to see Sane complete 20+ high intensity games with no notable dip in his speed once he returns.how do you know this?
In short it's probably August 2020 before he's sellable, and who knows what state he'll be in then or who'd be in for him?
He'll certainly have plenty of time to rue his refusal to sign his extension.