Not sure about Chelsea, because they only sold key players but at the same time, they didn't manage to bring in star players. Unlike Arsenal who managed to bring in great players in this transfer market, at least that is a big difference that I think Arsenal are still better at this moment. Moreover, Chelsea have a new coach and it seems too, the composition and or quality of the Chelsea squad next season is not so promising. Regarding Arsenal, although Arsenal have new players but the fact is they are used to playing in the Premier League. So yes, I believe Arsenal will be better than Chelsea for next season.
It seems that now Pochettino as the new manager has different plans compared to last season, he is very busy and does not hesitate to let go of players who even have an important role in his squad. Some of the top names that Chelsea have also sold are Havertz and Kovacic, both of whom have played crucial roles for Chelsea in the last two seasons. It looks like Pochettino will really start from scratch and now several new names have been brought in, one of which is Nkunku and Nicolas Jackson. The question is whether these new players will be able to keep up with the team's performance or further strengthen Chelsea's progress or vice versa. But apart from that, I have a bit of faith in Pochettino because he has quite a lot of experience in the Premier League, so I hope he has good reasons for his decision.
Actually I don't really want to compare Chelsea to Arsenal because maybe we all know that lately Arsenal are better than Chelsea, and maybe we shouldn't compare the two because they have their own problems and needs in every condition, and for now Arsenal are way above the Blues. For the Premier League next season, to be honest, I don't really have high hopes for Chelsea because in my opinion, with all the problems that are currently hitting them, it is certain that they will experience difficulties in the competition next season, and most likely Chelsea will not be able to provide maximum performance.