It looks like after two movies of running around not dealing with the politics of Asgard, Thor could finally have to do what his father Odin wanted from him in the first movie and take over the throne in the third movie.
With the recent rumor from Badass Digest that Avengers 3 could be without Chris Evans and Chris Hemsworth as a way to keep the actors around without having to restructure their contracts, it could mean the plot of Thor 3 will leave big implications for the God of Thunder and his future.
In the last movie, Thor left to be on Earth with Jane Foster and thought he departed with his father, Odin, on the throne when it was later revealed that Loki actually was there posing as the ruler of Asgard. With the events of Avengers 2 in question, it could end with Thor returning to Asgard after fighting Ultron.
The plot for the third movie has long been rumored to be Ragnarok, which would mean an apocalyptic situation for Asgard and the heroes that inhabit it. With this happening, it could lead Thor to have to stay after he settles everything down, which would leave him out of the events of Avengers 3.
It seems like the events in both Thor 3 and Captain America 3 could lead both heroes to take a break and have to deal with what is most important to them and this could lead to Thor making the decision to stay in Asgard and deal with the family matters that he hasn't been taking care of throughout the franchise.