Dragon Ball Super's climactic battle against Jiren the Gray served as one of the franchise's highlights. After a knock-down drag-out clash against Universe 7, the mighty warrior was finally felled thanks to the combined efforts of Goku, Frieza and Android 17.
Of course, Goku being Goku, he wasn't wholly satisfied with this conclusion. Having been robbed of defeating Jiren on his own terms thanks to his Ultra Instinct powers running out, he was forced to rely on his Universe 7 teammates to secure the victory. As he and Jiren parted ways, the Saiyan warrior made it clear that he wanted to face Jiren in battle again someday.
Has Dragon Ball Super Outgrown Jiren?
Several Super arcs later and said battle has not yet happened. Of course, Goku has continued to grow as a martial artist in the years since. While he struggled to maintain Ultra Instinct in his battle against Jiren, he has now nearly mastered the form, having used it in battle against foes such as Moro, Granolah and Gas. Given that an unmastered Ultra Instinct was enough for Goku to overpower the mighty warrior, it's hard to imagine that Jiren would stand a chance against Goku now.
Furthermore, Goku is not the only one who has faced Jiren and grown as a result. Vegeta has kept up with his competitor, even acquiring a transformation in the form of Ultra Ego that is comparable to Goku's Ultra Instinct. In Dragon Ball Super: Super Hero, Gohan and Piccolo gained power enhancements comparable to those of Goku and Vegeta, and Black Frieza, Frieza's new form, easily dispatched the Saiyan pair at the conclusion of the "Granolah of the Survivor" arc.
Jiren may have once been the apex of power among mortals in the Dragon Ball universe, but that time seems to have passed. Dragon Ball Super has charged ahead, introducing new characters, concepts and forms, while Jiren has been left behind in the dust. Does this mean Goku's promise to battle Jiren again was an empty one? While it's possible that Jiren has been rendered redundant as a character, it's still no guarantee that he'll never play a role in the story again. It's notable that, despite not appearing since the events of the "Universe Survival" arc, he has been mentioned on multiple occasions -- and still held up as an aspiration for Goku and Vegeta to match.
Goku and Vegeta Haven't Forgotten Jiren Yet
The first of these mentions came in Dragon Ball Super: Broly, when Goku was asked by Whis what's been motivating him to train even harder. Goku mentions the Tournament of Power, thinking back on all the opponents he faced, stating that if he has any hope of fighting them again, he can't stay at the same level. During this sequence, Jiren in particular is highlighted, and this by itself isn't too remarkable -- after all, Broly was the first storyline to take place after the Tournament of Power, and it makes sense that those events would be fresh in Goku's mind.
But when compared to Super Hero, a pattern begins to show. Vegeta is shown taking up meditation in the scene featuring Goku, Vegeta, and Broly's training on Beerus' planet; this is a characteristic of Jiren. Vegeta specifically notes Jiren's calm body and spirit as well as his capacity to maneuver effectively without wasting energy when Goku inquires as to why. The scene shows that Jiren still occupies a significant amount of the two Saiyans' thoughts despite them having faced formidable foes like Broly, Moro, and Gas in the interval. The post-credits sequence of the movie reveals that Vegeta was able to defeat Goku in their sparring battle by using Jiren's strategy.
It's noteworthy that both of these mentions happen in movies scripted by Dragon Ball creator Akira Toriyama. Toriyama's approach to Super's manga and anime interpretations has been more of an advisory one, which may account for Super's arcs being more self-contained than prior Dragon Ball series. While other Super-original characters have faded into the background, however, it's curious that Jiren remains at the forefront of Toriyama's mind, still an aspirational figure for Goku and Vegeta to overcome, even five years after the "Universe Survival" arc.
Moreover, even if Goku and Vegeta have surpassed Jiren's level of strength as of the "Universe Survival" arc, there's nothing to say that Jiren has remained stagnant either. Super has repeatedly shown that not being an active participant in the story doesn't preclude characters from having massive power boosts. Android 17, for example, is shown to rival Super Saiyan Blue in his sparring match with Goku, despite not appearing since the "Cell" arc back in Dragon Ball Z, and Frieza's powerful Black transformation was attained off-screen after the emperor's last appearance in Broly.
While it remains to be seen what kind of role Jiren might play in a future Dragon Ball Super storyline, there's nothing stopping him from coming back stronger than ever. It's rare for an opponent to stick with Goku and Vegeta the way Jiren has, and the repeated mentions indicate unfinished business between them. Should Goku and Jiren ever do battle again, their second bout will hopefully live up to the high bar set by their legendary initial confrontation.