Next season will be far more difficult because defending the title is not easy because there are many challenges that will be faced by PSG. For competition in Ligue 1 I am not so worried because there are almost no other teams that are able to break the dominance of PSG and overall the players they have are much better.
Yes, it will not be easy for PSG to defend their UEFA Champions League trophy next season because a lot of big clubs are serious in the transfer window, strengthening their teams, and it wouldn't be easy for PSG to beat some clubs in the next season's UEFA Champions League. For now PSG has no rival in the French league, and if they play with their second eleven, they will still end up winning the French Ligue 1 title because winning the French Ligue 1 is like their birthright.