Apparently it was just confirmed Joss Whedon,Adam Baldwin, Nathan Fillion, Ron Glass, Jewel Staite and Morena Baccarin are going to be at Dragoncon this year.
Addition confirmation from one of the track directors – “the official announcement was just made on the D*C directors list this afternoon; and before anyone asks yes all Joss’ panels will be in Centenial, he’s currently scheduled for one per day though this is subject to change. – Aaron”