A Sony sizzle reel that aired during a Twitch broadcast from the Taipei Game Show included an image hinting at a possible Metal Gear Rising 2.
The image appeared for a split second and contained nothing more than the number "2" in the typeface of Metal Gear Rising: Revengeance.
You can check the image yourself on Twitch. It appears at 2:46:39.
February 1, 2015 - 12:08pm