Cartoon Network’s Thundercats Site lists a new short to air December 6 at 6:58 PM EST on Cartoon Network. The 2-minute Thundercats short is called Snarf: Butterflies Blues.
More info as it becomes available.
UPDATE:
More info on the short courtesy of the guys at the Thundercats Crew Blog. When asked about the 2-minute short, they responded with the following (sections bolded by me):
“Snardf snarf snarf snarf story snarf snarf snarf before series snarf snarf watch for cameo snarf snarf not canon snarf snarf“