Their good performance gave them lots of rivals last season and some would be coming back for revenge this season so they need to be prepared for the challenge ahead it's not going to be easy cause Chelsea has exposed their weakness in the Club World Cup but I trust PSG to tackle that error, I'm suprise they didn't make much signings though.
Luis Enrique needs to strengthen his squad for the battle that's ahead of him, but if Luis Enrique decides he's not signing any player this summer, the PSG squad is still in pretty good shape, and Luis Enrique can compete in the UEFA Champions League with it and get good results. I heard PSG is interested in signing Rodri from Manchester City this season, but I don't know how concrete the news is.
PSG might be interested in signing Rodri, but that doesn't mean that Rodri will go to PSG. City needs him more and wouldn't let him go to PSG. The absence of Rodri affected the club a lot last season. PSG should know that no one can predict what will happen next season. They should have at least sign one or two players to add to the team for backup incase of injury.