After discovering that Zamasu wore a Potata earring which belongs only to Kais, Goku and the gang finally figured out that the Universe 10 Kai Gowasu’s life is in danger. Also, Beerus, The God of Destruction defeated Zamasu in “Dragon Ball Super."
“Dragon Ball Super” featured the story arc of Goku and the gang traveling to Universe 10 in order to protect Gowasu. Knowing that the future Zamasu was dangerous, they have to finish him in Universe 10. With the help of the God of Destruction, Beerus who also knows that the future Zamasu is dangerous killed the past Zamasu, according to Attack of the Fan Boy.
For now Goku and the gang felt safe for the future, but for Trunks, he feels uneasy and decided to go back to the past in “Dragon Ball Super." Black Goku was discovered of being in Zamasu's body. Zamasu discarded his own body and replaced it with Son Goku as per GamenGuide.
Now Trunks is the one who will face Zamasu in the future, being a Super Saiyan, Trunks transformed into Super Saiyan Pink in “Dragon Ball Super." Moreover, fans are hoping this transformation could level up with Zamasu’s power being the Black Goku.
While future Trunks of “Dragon Ball Super” urges Goku and Vegeta to go back to the past to find a solution to defeat the Black Goku whie he tries to prolong the battle and prevent the destruction of the world.