Tie ins to How To Train Your Dragon

What story elements needed to be tied in in next season?

- One of the storylines must explain how Astrid and Hiccup get together as they are a couple in second movie and there are rumors that they might get married in 3rd movie.
- At some point Heather must getting killed or getting lost because she doesn't appear in the movie
- I also guess that Raiders' base is getting destroyed.

My own television schedule contains all shows from Network, Cable and Hulu. Season starts June 1st.