Now i wouldnt consider myself a Marvel expert but i know a little bit. I developed a a quick theory in class one day based off other theories, and maybe this has been said before but oh well. What if in Age of Ultron when we see thors vision what if it wasnt the whole vision? What if he saw destruction and the coming of thanos to his home planet and also he sees Thanos paying the guardians a visit. Now lets say Thor and Banner and a side conversation, off camera of course, about how Banner wanted to get away and Thor needs help in the cosmos. Long story short Bruce Banner ends up in space and makes an appearance in guardians 2 to warn/defend against the incoming threat. While at the same time Thanos is literally destroying Asgard, hence the name Ragnarok, and plans to head to earth next. Which is how the guardians would tie into earth and so on. I realize this is a little far fetched but i think it would be cool. Let me know what you think and yell at me if this has already been said lol.