It seems almost certain now that he will leave, but I'd be surprised if Bayern made a move in January. Surely it would make more sense for them to leave it until summer to see how he recovers for the injury, and also because he'll only have a year left on his contract then?
The only reasons I could think of them going for him in January are Kingsley Coman's injury, and worrying that Sané attracts attention from other clubs in the second half of the season and in the Euro's, which given he'll be available relatively cheaply, could happen.
I guess it will come down to how certain they are that he only wants Bayern, and if he'll be the same player after injury.