Why do I have a feeling that Viktor is the one who will die in the end, because of some of the things they show in the teaser.
We see two hands reaching out for each other. And It looks like Luther's hands is one of them by the sleeve and the other is Viktor's hand 'cause of the orange powers that we see Viktor have.
And also the absolute devastation on the others faces in the van where we only see Klaus, Five, Lila, Diego and Allison. Viktor being the only one not there (Also Ben is not there, so he might also die) It might be just after the final battle and they see Viktor's sacrifices himself to save them
Not to mention that conversation Viktor have with Reginald can also be like a last minute deal Viktor is making to save the rest of the siblings. (Like bargaining)
I mean it also begins with Viktor starting the apocalypse so maybe it also has to end with him stopping it somehow.
(Also I have a feeling that Viktor still have his powers, maybe because of those powers he took from Harlan. But pretend that he don't and Reginald knows that which might be one of the reason they have a conversation )
But that is just a theory