While a third installment of Marvel's 'Thor' franchise has already been announced, specific details regarding the movie's plot or cast of characters have yet to be released. At this point, the only confirmed details are the title, "Thor: Ragnarok", and a projected release date of November 2017.
Lead actor Chris Hemsworth will return as the titular character while majority of the supporting cast are also presumed to return. Tom Hiddleston's Loki also looks to have a big role in the film stemming from the unresolved plotlines from 'Thor 2'.
The ending of 'Thor 2' showed Thor declining Odin's offer to take the throne of Asgard. Thor, however, is unaware that the Odin he was speaking to was actually Loki in disguise, signifying that his trickster brother is now effectively ruling Asgard behind the scenes.
The franchise is clearly trying to characterize Loki as having an ambiguous nature, with viewers left to wonder as to what his actual motives are. Regardless of what happens, the brothers Thor and Loki are expected to play a major role in 'Ragnarok'.
As for what the focus will be in 'Ragnarok', we can only surmise from the title that it will draw heavily from the existing notions of Ragnarok in traditional Norse mythology. Ragnarok is, of course, the Norse version of the apocalypse, and this kind of storyline seems to suggest a sense of finality, due to the world ending nature of apocalypses. Still, whether 'Thor 3' will be the last of the series has yet to be determined, but it should certainly attempt to close the "trilogy" with a bang.
In related news, recent Marvel movies have featured appearances from other characters in the Marvel cinematic universe. In 'Captain America 2', Black Widow and Nick Fury play key roles, while the upcoming 'Captain America 3' features Iron Man in a major role. Will 'Thor 3' have something similar? So far nothing has been announced, but the potential is still there.
'Thor: Ragnarok' is expected to be released in November 2017 in theaters worldwide.