Tough choice actually. I would say it's somewhere between Baron, Cannibal and K?????rnan.
K?????rnan would already drop off since they are finishing theming for 2016.
Baron is already looking great, same goes for Cannibal. Knowing the Efteling. Baron will get a great full story with a decent dive machine. Cannibal on the other hand I don't know. But I still think the theming from Cannibal is going to be more interesting for me (Despite the ugly looking tower
)
I'm picking Cannibal for this one.