He might be leaving after all. Showed really poor attitude against Burnley.
He clearly has some issues regarding his attitude and overall focus, if you are to believe Pep and Joggi Löw; his talent and capabilities are undeniable, but elite sports more often than not rely on the mentality and state of mind of professional athletes rather than ability. Obviously talent and physical attributes are basic necessities to compete at the highest level, but it is the mental driving force that ensures competitive edge and overall succes.
This could however all be to our advantage; we are a club capable of 'containing' big egos with the right environment and setup from top to bottom; we should go all in for Sané, we will not get another 'window' were the chances of acquiring him are this high (not that they are that high anyway) - his lack of playing time and his semi-cold relationship with Pep could open the door for us. His contract runs until 2021, which gives us room to negotiate a deal if he were to push through.
All of this is speculative and the club clearly seems to be weighing up other options such as Griezmann (proven La Liga player, WC winner, technically gifted, lives in Spain and speaks Spanish fluently), but I would prefer it if we went all in on Sané, rather than throwing 120 mil euros on a player in decline, who showed us the middle-finger only a year ago.