Dragon Ball Z: Kakarot is a quite chunky open-world game which could mean some players will get impatient eventually and decide to progress the main story instead of side quests. The new Time Machine feature will give them an opportunity to replay these.
Depending on which part of the game the players are in, certain Dragon Ball Z: Kakarot's side quests might not be available to them. The correct term would probably be the players' position on the timeline but this can be changed by using the Time Machine that Bandai Namco added in a free update.
To gain access to the Time Machine, players will need to help out Arale and Gatchan in a new sub-quest. Upon completing the activity, it will become available for usage and they can move back in time to previous story arcs in order to complete the quests they missed out on.
Fans who are wondering how this might fit into the universe shouldn't worry too much. The feature is non-canon and the story arc and future Trunks' arrival should remain intact. In the case of this time machine, it is there just to let completionists do their thing but it remains to be seen whether Bandai Namco have something else up their sleeve in order to tie it to the rest of the universe properly.
Back on the topic of future Tunks, fans are already calling for a more persistent presence of fan favourite characters, or rather fusions of characters - Gotenks and Vegito, especially since the play a big part in that saga.
Fans also took notice of Bandai Namco emphasising that the update is free, which could mean future updates might not be. Then again, depending on the size of the updates, these could by fully-fledged DLC packs, spanning across story arcs that already played out in the anime.