They believe that Jujutsu Kaisen will have a sequel manga

Recent leaks have ignited expectations among fans of "Jujutsu Kaisen," confirming that the final chapter of the manga, scheduled to be published on September 29 in Weekly Shonen Jump magazine, will include several "happy announcements." According to these reports, author Gege Akutami will say goodbye to the series with a large color illustration and a special announcement that has been described as a gift for fans of the work. In addition, the editor of the series has contributed to increasing speculation by declaring that "there will be more of Jujutsu Kaisen to come", which has unleashed all kinds of theories about the future of the franchise.

One of the most discussed points among fans is the possibility of a direct sequel. While Gege Akutami has reiterated on several occasions his intention to finish the manga as soon as possible, these new statements have fueled the debate about whether the end of the manga will really be final. Many fans believe that the plot has been resolved abruptly in the last chapters, which has generated some dissatisfaction among readers. However, the publisher's announcement has left open the possibility that Jujutsu Kaisen will continue in some way, whether with a spin-off, new spin-off stories, or even the expansion of its universe into other formats.
Despite this, several fans maintain a more conservative stance, remembering that similar cases in other franchises, such as "My Hero Academia", generated excessive expectations. On that occasion, a "big announcement" was also promised to accompany the final chapter, which ultimately turned out to be a popularity poll, which caused disappointment among many followers.
Jujutsu Kaisen is one of the most successful series of recent years, with a great impact on both its manga and its anime adaptation. Currently, a third season of the anime, which adapts the Sacrificial Game Arc, is in production, but there has been no recent news about its trailer or possible premiere dates. This has led many to speculate that the "happy announcements" at the end of the manga could be related to the anime.
Although a direct sequel seems unlikely given Gege Akutami's focus on closing the main story, it is evident that Shueisha and the anime's producers still see great potential in Jujutsu Kaisen. Fans will be keeping an eye out for September 29 (or probably leaked much sooner), waiting not only for the closure of an era, but also for the start of new adventures within this universe that has captured the imagination of millions.
Source: WSJ Manga