Previous reports have claimed that Future Trunks will be asking for the help of Son Goku, Vegeta and their friends to help him fight a new nemesis that threatens the peace of the future world. Out of nowhere, an adversary called Black Goku has come out.
This, then pushed Future Trunks and Future Bulma to travel time. However, Black Goku has reportedly captured them so they won't get help from the people in the past.
What makes the character of Black Goku more interesting is the fact that his powers and skills have no match with other Super Saiyans. In other words, Black Goku is a very huge threat that Goku, Vegeta and friends have to beat.