Seeing as Marseille drew at home , Messi's 90th minute assist made PSG go +10 points on top
PSG will win the league that's not even questionable. However, despite that, their season is already a big failure. They should heavily rebuild in the summer.
Skriniar should be a good option at CB. Midfield is where they have always lacked quality. Getting established names is tough. Plus I think they need some options on the wing and striker.
Sensible thing to do would be to sell Neymar to Chelsea and don't renew Messi. They clearly don't know how to integrate these players in a team that wants to make Mbappe top dog. Neymar is always injured anyway.
Skriniar will be a good option. However, the biggest problem is midfield. They need at least 2 great midfielders to be competitive in Europe. Furthermore, If they sell Neymar and don't renew Messi they will also need 2 good forwards. I sincerely doubt that they can have a competitive squad for the next season. No one can address all of those problems and bring 5 or 6 quality players in one transfer window.
They will probably move Mbappe to the wing and go for Bernardo Silva and Osimhen. However, I don't think those two will be enough to successfully compete against top CL teams.