Ganked from the LJ mst3k comm:

Shout! Factory has announced the bonus items for the 20th Anniversary DVD set: Film trailers for some or all of the featured episodes, a "History of MST3K" featurette, and a recording of the 20th Anniversary panel at Comic Con. Don't know what "recording" means, but I hope it doesn't mean "audio only", because that would be odd.

http://www.tvshowsondvd.com/news/Mystery-Science-Theater-3000-Anniversar-Bonus-Material/10090