Defeated by Chelsea in FIFA club world cup doesn't mean to remove the status of PSG as one of the best team in the world. PSG is still one of the best teams, it remains one of the biggest candidate of the UCL champion in the next season. Regarding Chelsea poor performance in the previous season, it can't be your reason to determine their performance nowadays. During the break of the season, Chelsea has improved many things. It includes signing some new good players. So, when they played against PSG in the FIFA club world cup final, it was no longer the same Chelsea squad in the previous season.
This is football, and it's always hard to predict who will finish first. 😁
After PSG title success last season, they certainly remain a contender, but they're not necessarily the strongest contender.
Next season, we don't know who will be the strongest contender, because even if every club recruits new, high quality players, it doesn't guarantee a title win.
But everyone has their own speculation, and in my opinion, I'm looking forward to Barcelona winning the title next season, as last season's experience suggests they're ready for a stronger challenge.