Dragon Ball Super is currently in the midst of universal survival arc, with the Tournament of Power raging on. However, fans may have already been given a hint to what will be coming next in the series.
In episode 93 of Dragon Ball Super Universe 7’s angel Whis stated, “there is a universe where lives a mortal even a God of Destruction can’t defeat”. Many fans believed that this might have been Whis warning Universe 7 of a warrior competing in the Tournament of Power, however that may not necessarily be the case.
From what fans have seen in the Tournament of Power to date, the only character Whis may have been referring to is Jiren, although; it is too early to confirm this. Universes 1, 5, 8 and 12 are not competing in the Tournament of Power, as their mortal level is acceptable according to the two Zeno's. This also means that there are warriors in each of those four universes that fans haven’t seen yet. Therefore, it is possible that Whis was referring to a fighter from one of those four universes, which could be a hint for what is to come in the next arc of Dragon Ball Super.
If the mortal fighter that Whis was referring to is in one of those four universes, fans won't see him/her until the Tournament of Power has ended. Being a warrior who is stronger than a God of Destruction, means that he may thrive on fighting; similar to Goku. As a result, this unknown fighter may wish to meet or battle with the winner of the Tournament of Power, as Goku would want to do as well.