Zamasu is indeed dead so the future should really be secured that is according to Beerus. But in "Dragon Ball Super" Episode 60, viewers will find out that Zamasu and Black Goku are still alive and that the future is still not secure.
The start of "Dragon Ball Super" episode 60 have Future Trunks doubt Beerus, as the god already killed the present Zamasu. However, Trunks still feel nothing has changed in his future since he is still there with them in the present timeline.
He wanted to leave and go back to the future together with Goku and Vegeta but Bulma insisted to having dinner first to which Future Trunks obliged. Once the dinner was done, everyone head to the time machine.
In a very complicated explanation on "Dragon Ball Super" episode 60, Future Trunks explains to Kid Trunks how his future may still be the same and nothing probably changed. As the two look into the city, Future Trunks explained that the city where he grew up in and the city of Kid Trunk are different.
They live in two different timelines where Goku, Vegeta, Piccolo, Kurin and Bulma were already dead. Goku dying from a heart virus and Vegeta being killed by the androids 17 and 18, six months after Trunks was born.
Future Trunk, however, was able to destroy the androids 17 and 18 and explained that the 18 who married Kurin and had a child with him is totally different from the 18 of his world. To this they realize that there are more different worlds out there than they think.
Once everyone was ready to board the time machine, Bulma decided to come with them. Although, they were all cramped inside and Goku was insisting for Bulma not to come but Vegeta knows that they will not win over Bulma.
Goku, Bulma, Vegeta and Trunks now went to the future in "Dragon Ball Super" episode 60 and found out that nothing changed. Once inside the camp, they find out that Mai's life is in danger so they had to give her a Sage Bean to cure her.
Zamasu and Black Goku also knew that Goku, Vegeta and Trunks are back and went to meet them in "Dragon Ball Super" episode 60. Vegeta wanted to have a plan first before they attack but soon had the urge to just go and attack Black Goku which he says was the plan.
The big revelation of "Dragon Ball Super" episode 60 was that when Black Goku finally says that he is indeed Goku and with the same body. He has the body of Goku but the heart of Zamasu. They switched body and killed the real Goku.
In "Dragon Ball Super" episode 61, Goku, Vegeta and Trunks finally understand how Zamasu and Black Goku becomes more powerful when they are together is because they are one and the same. They will search for a way to defeat the two gods.
Also, in "Dragon Ball Super" episode 61, more will be revealed in Zamasu's plan in totally annihilating all humans. More will also be revealed on his hatred for all living creatures in "Zamasu's Ambitions: The Terrifying 0 Mortals Plan."
