Too late for him to leave. I don’t even understand Bayern’s raging hard-on for Sane. Other than being German he is not going to turn them back into the dominant force they were with Robben and Ribery. There a lot of alternatives that they could have signed but they wasted all summer fantasising about Sane.
Now on the topic of Sane’s decision, he is still a rough diamond. He was abused by German fans (+Bayern) for his abysmal performances for the national team pre world cup and he will be blamed at Bayern because he is far from being the finished product. We are a lot more lenient with Sane’s performances but if he were to have a season like his previous at Bayern, their fans would have their pitchforks out. Obviously it is his decision but I sincerely hope he tries to develop into the player he is supposed to be rather than running away.