I think the Hulk works in small doses. Like Dee, I enjoyed the Norton Hulk, but Ruffalo nailed it. How much plot can you derive from a dude that breaks things in spectacular ways?
Thanos will have a cameo again, but The Collector is the main baddie. Panther is not going to netflix. Black Widow's scenes had to be fast tracked in the Avengers sequel, she done got knocked up.
Rick became what he had to. I liked the discussion they had on Walking Dead where Rick came to the point that it's an ugly world and you have to do what's necessary to survive.