Okay, so I'm just gonna say what I think will probabbly happen in the next few episodes, starting with the the 100th episode.
100th episode- So everybody is guessing that Katherine will eventually die. Well I think not. I think she will die but be turned into a vampire or something or is saved by a witch idk? Maybe Wes takes her and does a deal with her, she is turned into a different type of vampire and has to do his bidding? Idk, but I'm pretty sure she won't die or maybe she will but will come back as a new breed of vampire.
Traveller Storyline- So we've also learned in 5x08 that the Travellers are after Katherine. I think that the Traveller storyline will tie in to the vampire expermintation storyline somehow (they think it's breaking the rules of nature maybe?). I also think that the Travellers will be the new Kitsunes/Malach of the show, they can possess people.
Wes/Experimantation Vampire Storyline- Wiping out vampires out of the face of earth is probabbly the cause of this OR Wes is engeneering vampires who don't need to drink human blood and instead be immortal forever. Probabbly they will also tie in a new cure with this storyline.
The Augustine Vampire Storyline- Grayson may turn out to be the one who taught Wes how to experiment. Damon will maybe turn into an augustine vampire via Enzo? I REALLY AIN't SURE WHAT TO SAY BOUT DIS STORYLINE CUZ DER ARE TOO MANY CRAY THEORIES.
Conclusion:
I think that the next few episodes are mainly going to focus on the augustine society, from episode 5x11 and up they will probabbly start making way for the Traveller storyline.