Unfortunately, these boards have been taken down :(
Remember how we learned that the characters would be five years older in the sequel? Well, here are some recently uploaded sketches by Tom Owens that feature Hiccup and Astrid as adults.
It looks like two of his posts from today and yesterday are from the same Hiccup and Stoick scene. Perhaps this is from the sequel, or cut from the sequel?
In addition, there are several recently uploaded sketches of Hiccup, Astrid, and Stormfly.
(Read these from the bottom-up.)
Also, according to kris0ten, adult Hiccup and Astrid will be very hot.