A lot of strong fan theories have already come to pass (or well on their way), we're just seeing the journey to get there.

That said, there isn't a ton of firm theories on Littlefinger (that I've personally seen, at least) so his eventual fate is still up in the air. I'm going to be paying super close attention to his scenes because while the books and show will differ in how they get there, his endgame is so wide open.

I still love that he's been the great architect for the most pivotal events in the show yet no one really knows this.