Board Thread:Manga/@comment-24930713-20150810080743/@comment-5774380-20150811180832

89.134.134.66 wrote:

Speculation: Erwin will receive the Titan serum and will fight the beast titan. Levi will die before the story's conclusion.

Isayama can't kill Levi because he is the most popular character of the series and the fandom would hate him (he didn't kill Sasha as he originally planned for the same reason). But I do think that either him or Erwin will receive the Titan serum.