I can't say if Chelsea has improved in their performance or not, it's when the new season starts is when we would know. However, their performance in CWC is impressive and their fate will be tested in the finals when they play against PSG who have destroyed and humiliated top big clubs in various leagues in recent times.
The season haven’t started yet, so we can’t conclude yet that Chelsea performance has improved, but even as they have been playing against weaker teams in the FIFA club world club, I can see that Chelsea performance has improved a little bit. The Chelsea which I know few seasons ago, even when playing against weaker teams, their performance is always poor, but with Chelsea players are now having confidence when playing, not like before that we are going to see them making mistakes.
Indeed, we can't say Chelsea performance will be all good this coming season, even when the cwc performance is really good. I remember under Poch we did well at pre-season but fell continually in that season. Although, our players has greatly improved but that doesn't disrupt the fact other top teams are strengthening a squad, even the same one we find difficult to oppose/defeat last season.
Let's see how they perform. When the season starts, seeing their performance and consistency.