According to a report from Sport Bild (as captured by @iMiaSanMia), Bayern Munich manager Julian Nagelsmann wants to lead a “tactical revolution” at the club and will likely initiate change by the full implementation of a back three system:
Julian Nagelsmann wants to shape an era at FC Bayern with his back three system. Unlike all Bayern coaches since Louis van Gaal who mostly relied on 4-2-3-1, Nagelsmann initiated a ‘tactical revolution’ and plans on stabilizing and keeping it on the long term.
Nagelsmann has been leaning this way for quite a while and the club’s renewed interest in inking Benjamin Pavard to a contract extension indicates a chance might be happening. With four starting-level center-backs required for coverage on the roster, Pavard would conceivably join a rotation that would include Matthijs de Ligt, Dayot Upamecano, and Lucas Hernandez. Josip Stanišić is also a candidate for a center-back spot in a back three as well.
The backline is not the only area of the squad that would be affected, though. With four starting caliber wings on the roster, it can be assumed that not all of them would be be needed.
Who would go among Sadio Mané, Kingsley Coman, Serge Gnabry, and Leroy Sané? Mané could possible play a role as a striker, while Coman (wing-back) and Sané (attacking midfielder) could also be set for new (or at least updated) positions.
As for Gnabry, he could play a number of positions, but it likely will come down to whether or not he wants to take his chance at moving to another spot.
Whatever happens, a shift to a back three will necessitate some change in personnel.