I think that after the first games without Lewandowski it will be clear what shape Bayern are in, but I also think that the coaching staff at the club are not fools, and Mane has been selected according to certain requirements... Most likely he will be able to perform as well as he did at Liverpool... By the way, Bayern remain the favourites for the top spot in the Bundesliga for many...
With Lewandowski or not in the Bayern Squad, he will still be the favorite in any case because this is a real certainty 
Actually I hope this will be fast because I want to see what kind of game they want to do in the future whether it will make Mane's position more special to be a Targetman like Lewandowski or not because actually having him on the front lines makes the enemy still very uneasy safe even without Lewandowski.