I don't belive Sane will join Bayern. The case Götze showed, just because Bayern wants you, it doesn't mean the manager wants you. Bayern want Sane because he is a huge talent and german, fits perfectly into the clubs philosophy. At the same time, Ancelotti (who is an excellent manager) is not known for promoting young players. It's not him to decide which players will join Munich, but the likes of Rummenigge&Co.
With Guardiola, we on the other side, got a coach which is known to promote young talents and give them enough game time. Pep did it right in front of Sane, giving players like Kimmich and Coman massive game time and chances. If City are interested in him, Sane knows it is only Guardiolas decision.
A further big plus is the Premier League. I'm german and I think the Bundesliga has some good teams and players, but f*ck me, the development of the league is shocking. The most amazing in this league is the battle of relegation. Dortmund, the only real threat to Bayern, have once more lost a key player. Gündogan left them, Auba and Mhiki could follow. The odds for Bayern becoming Champions next season are 1.15! Of course Bayern are an absolute top club, but I think you have to win the Champions League to be happy there. And no team in the world, not even Barcelona can guarantee international success. What's great about winning a league or a cup every year when you got zero competition? On the other side we got City, United, Chelsea, Arsenal and so on.
I'm sure, if he has to choose it will be us.