Considering how the sire bond comes from hybrids feeling grateful for no longer having to endure the pain of turning into werewolves, if they wish, shouldn't this mean that Elena too could be gifted with this gratitude?
AU Scenario: All the terrible things the fans have been speculating will happen this season happen. Damon dies. Stefan continues being a dominating, judgmental, backstabbing douche who keeps aligning himself with the Originals. Jeremy dies in order to find the cure. Bonnie survives, but her Expression magic has made her all the more intent on growing her power base. Silas is risen, Silas raises the dead. ZOMBIE APOCALYPSE ENSUES.
Well, after losing both Damon and her brother Jeremy, Elena's so emotionally devastated that she needs to "turn it off", i.e., she willingly chooses to become the cold-blooded manipulative force of nature she could always be when needed. Bonnie's there by her side, but Elena needs to up her game or she's not going to survive and she has to survive now or else her loved ones' sacrifices become meaningless. Of course, this means NOT taking the cure that would turn her human again (reading this straight, okay?), the cure which she and Bonnie are in sole control of after having tricked the Originals into thinking it had been destroyed.
On the run from zombies, Bonnie and Elena concoct a plan to track down Katherine and join forces with her... only not in a way Katherine would ever willingly choose. Having realized that the hybrids could also be sired to Elena, Bonnie and Elena trick Katherine into taking the cure (better Katherine than Elena, ok, flipping that rationale in Katherine's face) and once she's human again, they use her blood to make a hybrid army to fight Silas and his zombies. Turns out it's easier to convince werewolves to turn into hybrids when you explain how it makes them harder to kill in a world overrun by the dead.
So yeah, DARK END OF THE WORLD shit where Elena and Bonnie are Generals fighting the war against Silas. Also at some point, Elena captures Stefan and tortures him because why not.