Outgoing manager Carlo Ancelotti eventually settled on a Brazilian-inspired 4-2-2-2, with attacking midfielders Javier Pastore and Lucas Moura playing much more centrally than is the norm. Fullbacks provide necessary width, but the formation occasionally seemed disjointed, without proper numbers in midfield.
This 4-3-1-2 fixes the midfield numbers issue. Once again the full-backs are called upon to provide width, while Javier Pastore is slotted deeper into central midfield. Not his preferred position, but he appeared there four times last season, notching one assist, so he's proven to be comfortable there.
Pastore also attempts a lot more long balls per match (2.9) than the more natural No. 10 on the squad, Brazilian Lucas Moura (0.8). He also averages more tackles (1.8) than any other PSG attacker. A deeper position ought to suit him just fine.
Finally, note this observation from Bleacher Report Featured Columnist Max Towle, taken during the recent pre-season friendly with Real Madrid:
5'- Some early possession for PSG in the opening stages. Javier Pastore drops back to get some touches of the ball.
Whether the formation changes officially or not, the team's offense already gravitates towards this model.