Death is something that has been almost nothing but cruel and tragic in the world of Attack On Titan. ... It is there, we meet Erwin and all of the dead comrades of Hange. And even a horse. It is the first time where the afterlife has been shown in SNK.

Can Eren from AOT see the future?

It turns out the Attack Titan has a power which no one ever knew about, and it is changing the way fans are viewing Eren's seemingly dark turn. ... "The Attack Titan is capable of seeing into the memories of its future inheritors. In other words, it is capable of knowing the future."

Is Eren permanently dead?

At the end of Chapter 138, Mikasa was about to kill Eren. A flurry of events that had been occurring in the last few chapters and episodes suggested that Eren had taken a turn into the dark side. Hence, unless there are plot twits at play, it looks like Eren Yaegar is indeed dead.