San Diego Comic Con? definitely. i'm not sure how much sci-fi is in other comic cons, but the one in San Diego definitely has a presence. Sci-fi channel (Syfy) has their own booth where they give out promotional freebies and probably might have guest appearances. Upcoming sci-fi movies and TV shows also present in panels with preview clips and Q&A with the cast and crew. Plus Star Wars has its own day at SD Comic con on Friday when most panels are about Star Wars.
If you're asking about cons around New England, there's Wizard World New England Comic Con. Wizard World cons are also pretty popular and huge. The company owns the magazine Wizard that focuses on not just comics, but also movies, anime, toys, collectibles, game cards, and such. Sci-fi shows and movies are featured as well. So, their cons most likely showcase the same as their magazine.