Board Thread:Manga/@comment-24930713-20151109044731/@comment-5774380-20151109225556

Well, discounting Eren, there are at least other 3 Shifters there available to be eaten; and I say "at least" because we don't know where Ymir is, and the Quadrupedal Titan is possibly a Shifter too, so there are chances for Levi or anyone else to be injected with the serum, eat one of the invaders, and turn into a new Shifter.