I said this long ago, there's obviously a reason why Kishi didn't just kill him off.
First Yamato will make his comeback and it will be revealed that he is the true reincarnation of Rikodou! Then he'll go Rikodou Mode and stomp Madara, but then Hidan will make a comeback and use the true power of Jashin to take on Yamato in the most epic fight in the history of the universe!!!
Obito was just a bridge to madara and madara will also be just a bridge to the true final villain... the ichiraku ramen guy. He saved madara after the fight with hashirama and planned everything evil happened in the naruto universe.
Actually, Hidan was one of the lamest villains (or characters in general). He is as much final villain material as Tonton.
And people are really overinterpretating that Jashin-stuff. There isn't a true being like that, it was just Hidan's belief and excuse for his insanity. THat's all.
The final, main and true villain of this series was, is and will always be Madara.