If the rumours are to be believed, we're going to replace an underperforming bench player, who has probably reached his ceiling, by a potential starter and worldclass AM/forward in the making. I don't see any reason to be worried. On the contrary, this transfer will make us only stronger.
I reckon Guardiola can't wait to get rid of Sane - he's probably our weakest player (not named Kyle) in terms of footballing IQ, spacial awareness and interplay, he hasn't shown any significant improvement this year, his attitude stinks. I didn't expect Sane to be so one-dimensional when City signed him, but here we are after 3 years. Cash in and move on.