One of the complaints I've heard regarding T:TDW is that it focused more on Loki's character arc than Thor's. Whether that assessment of T:TDW is true or not, I hope they approach Thor 3 from Thor's character growth.
To that end, I think Thor will make the personal sacrifice and end up on the throne of Asgard by the end of the film. I think Odin will die, Loki will be revealed as the villain he is AGAIN, and Thor will realize that he has to put the needs of his realm above his personal desires (or Jane dies, too, and Thor has less of a personal reason to stay on Earth...). We could get a more mature Thor out of this, and it seems like the only logical way to go.
Also, I think a ballsy move on Marvel's part would be to do a "Reigning"-style story for Thor 4, if one were to happen (Thor parks Asgard above NYC to better protect Midgard.). I've been thinking a lot about compelling ways to take Thor's character forward in the MCU, and something like that would definitely be a bold step.
Of course, a close adaptation of The Reigning wouldn't really work for many, many
reasons, and I don't think it's the only way to go if Thor does end up on the throne at the end of Thor 3... it was just a passing thought.
Regardless of Thor 3's plot, where would you guys like to see Thor's character arc/conflict/growth go in the next movie(s)?