The reason why Kane didn't leave Tottenham earlier was Conte's arrival at the team. They have done a really good job with Conte so far. However there are some rumours like Juventus might be thinking of bringing Conte in case Allegri maintains an unsuccessful season.

If this really happens then this would affect Kane's decision to stay or leave as well. I think Kane's decision would be to leave. Kane has been accustomed to English football for so many years. Maybe as you indicated, his first option might be to stay in England. But I still don't think he would prefer Manchester United over Bayern Munich.