The club already expected to have a new coach in upcoming season. PSG will be making some movements during the summer transfer season. PSG just let galtier to end this season in PSG. Galtier is not as good as people think.
Hiring another coach is not enough for PSG. They must to rebuild their squad and make it more balanced between attacking and defense. If their squad continues to be not balanced, no coach can help them to win Champions League.
PSG already bought some world class players and that's not enough to win UCL PSG. To be honest if the performance from PSG this season is disappointing for PSG fans. Galtier will be sacked or he must be leaving the club by himself. I would not be surprised to see that PSG has been offering some good coaches to join the club.
They have world class players but their squad are imbalanced that makes them weak when they play with big clubs in Champions League. Such imbalance is not a big issue in Ligue 1 but in Champions League, it is their dead weakness.
Messi is already rumored to go back again to the barcelona.
I believe he won't. Barcelona current president Laporta treated Messi badly and he has no reason to rejoin them. Moving to Saudi Arabia Professional League and grab huge salary in a last few years of his career is more interesting for him and his family. In addition, returning to Barcelona might not bring more happiness to Messi and he will get more pressure there.