Appearing incredibly briefly in a Sony flavor reel shown during the Taipei Game Show, this is definitely the sort of two one might expect to find following the words "Metal Gear Rising."
While Metal Gear's big boss Hideo Kojima didn't mention a follow-up to the over-the-top crazy that was Metal Gear Rising: Revengeance during his appearance at the show, fans have been pointing to this blink-and-you'll miss it digit from around 2:46:39 in the Tapei Game Show Twitch broadcast (via NeoGAF) and Kojima tweets about a visit to Platinum Games late last year as proof that a sequel is in the works.
Without confirmation it's just a fancy number two that would be right at home on the case containing a sequel to Mr. Raiden's Opus.
UPDATE: The rumor was debunked by an official tweet.