Loki dies--maybe. I'm not really sure. That's what I wanted to discuss.
To be a little more on the nose, there's a fight scene about two-thirds of the way through the film where Loki is apparently killed, then a few scenes later, we see a guard who's clearly him in disguise get up from the spot where his body was left and return to Asgard. The payoff for this is a reveal of Loki sitting on the throne of Asgard in Odin's place at the very end of the film. We can probably all agree that the God of Mischief was carrying out some kind of scheme the whole time, but what viewers do disagree on is whether Loki just faked his death or actually died and somehow came back to life. The movie doesn't explain, so we pretty much have to speculate about what happened until the next Thor installment comes out.
First, there's the theory that Loki just faked his death. That seems more likely since obviously, it's a lot easier for someone to fake death than to come back from it. Another obvious point is that Loki is a master illusionist who can magically alter his appearance whenever he wants. That would explain how he was able to look fatally wounded and turn pale as he seemed to fade out. On top of that, he can alter other people's appearances too, which could mean that the villain Kurse impaling him through the chest was also an illusion. For all we know, the real Kurse could have been standing around in confusion with some sort of invisibility spell over him while that fake image was playing out.
There's just one problem with this idea. Illusions can only make a person look dead; they can't make a person feel dead. I know Thor isn't very bright, but don't you think that a thousand-year-old warrior like him would at least know how to detect vital signs? He even had his hand under Loki's neck--one of the places where you can feel someone's pulse--all throughout his brother's death scene.
Granted, Thor was pretty upset at the time and might not have noticed that little detail, plus a huge sandstorm was starting up that forced him and Jane to move on and look for shelter right away, but Loki had no control over those factors. He already knew from his prison-break scene that Thor had learned to recognize his illusions, meaning there was a chance that Thor wouldn't fall for that trick again, and it's very unlikely that Loki planned for that sandstorm to start right after he faked his death. Considering that, it seems like he had no plan for how to get Thor away from him before those pesky vital signs could give him away. Could that be because he wasn't planning for his death to be fake?
That brings us to the other theory, that Loki genuinely died in the fight with Kurse and then resurrected shortly afterwards. Probably the biggest reason why people side with this idea is because something similar did happen to Loki in the Marvel comics. In that storyline, he was able to come back to life because of a deal he'd previously made with Hela, the ruler of the underworld, to have his name removed from all of her books. Having his name removed basically meant he had no more appointments with death and was therefore immortal, and he used this advantage in a scheme that involved him dying and reincarnating to throw the other Asgardians off of his trail. It would make sense if this was also the case in the movie, because then he wouldn't have to worry about casting any illusions. It's easier to really be dead than to act dead.
This wouldn't be the first time a character resurrected in the Thor films, after all. The God of Thunder did it himself in the first movie, and seeing how Loki has a knack for magic and inter-realm travel, it wouldn't be a stretch for him to manage the same feat. In fact, in the scene in The Dark World where Loki gets back up in his guard disguise, he appears to be winded or disoriented. It would seem odd for him to be in such a state if his battle injuries and death were faked, so this could be a sign that he really was recovering from something very painful or jarring. Also, the realm of the dead in Norse mythology is known as Hel, so Loki's line right before he kills Kurse may have actually been, "See you in Hel, monster!" rather than, "See you in hell, monster!" He could have literally meant that he was going to see Kurse face-to-face again in the underworld in a few minutes--and maybe even rub a good-bye in Kurse's face on his way back out of Hel.
Just like with the first theory though, this idea has one problem: why in the world would Loki ever take such a huge risk and actually let himself be killed? How did he know his plan to resurrect would work? Assuming he'd made his deal with Hela just like in the comics, how did he know she would uphold her end of the bargain and not decide to lock him up in Hel after all? I don't know much about Hela as a character, but isn't the ruler of the underworld in just about every religion and mythology prone to making loaded deals with tons of loopholes that they can exercise to get what they want? I suppose if anyone can outwit the ruler of death, it's Loki, but that still seems like a huge, unecessary gamble for him.
Even so, I still find myself leaning towards the resurrection theory. There just seems to be more source material behind it, plus it would open the movies up to feature Hel as one of the nine realms in the next installment. This is all speculation of course, so I could turn out to be completely wrong on opening night of Thor 3, but that's the fun of theory rants. They're a brain exercise, and in some cases, they can even leave you with some interesting, original ideas that you can integrate into your own writing.
And whatever did happen to Loki in Thor: The Dark World, it's a good thing Thor didn't bury him. Wouldn't that have had a funny implication later in the movie?