According to reliable sources, the next Dragon Ball Z: Kakarot DLC after the Bardock Saga will be an adaptation of the 23rd Tenkaichi Budokai Arc. This particular story saga is the last one of the original Dragon Ball and is perhaps more commonly known as the Piccolo Jr. Saga. It introduces the beloved Namekian fans know throughout Dragon Ball Z as simply Piccolo. Dragon Ball Z: Kakarot will release native PS5 and Xbox Series X versions on January 13, as well as the Bardock: Alone Against Fate DLC. This DLC is the first of the game's second season pass, which developer CyberConnect2 and publisher Bandai Namco Entertainment announced in 2022. The other two DLC have yet to be announced, and while this Piccolo Jr. Saga leak should be taken with a grain of salt, it comes from a source that was right numerous times throughout the first season pass and general development of Dragon Ball Z: Kakarot.This news comes from Twitter user DBSHype, who says their source has "double confirmed" this claim as made by another Twitter user. All of this makes this more reliable than a standard online leak, but again, this has not been announced yet. It'll likely be sometime after the release of Bardock: Alone Against Fate that fans get official information. At large, this saga covers Goku's training with Kami and the World Martial Arts Tournament against Piccolo Jr as his reincarnation of King Piccolo (and follows the preceding King Piccolo Saga). The next saga after this one is the Raditz Saga, or where Dragon Ball Z: Kakarot (as well as the anime and manga) officially begins.
​Furthermore, it features a couple of fun fights, such as Piccolo vs Hero, and plot developments for Dragon Ball Z. For example, this is where Goku meets a grown Chi-Chi, not recognizing her at first, but eventually proposes to her to follow-up on his promise.
It's worth noting that there are also rumors that Dragon Ball Z: Kakarot will get a similar DLC treatment to Dragon Ball Xenoverse 2. As many fans know, the latter has received a constant influx of DLC since its release, so it stands to reason that Season Pass 2 may not be the last one for DBZ: Kakarot. It does remain to be seen, of course, but there are plenty of story sagas not available yet in DBZ: Kakarot.
Dragon Ball Z: Kakarot is available now for PC, PS4, Switch, and Xbox One. It will release on PS5 and Xbox Series X/S on January 13, 2023.