Update
Since the first reports started springing up, journalist Geoff Keighley has Tweeted: "Slice that rumor: No Metal Gear Rising 2 tease at Taipei games show. Spoke to @Ken1555 from @Kojima_Pro_Live, it is not true."
Original
A sizzle reel shown by Sony at the Taipei Game Show in Taiwan may have included a second-long tease for a possible Metal Gear Rising sequel. It's a blink and you'll miss it affair, but as you can see from the screen (grabbed and posted on Neogaf) the font used for the number "2" is remarkably similar to that used in the first game's main title. Make of that what you will.
The original game in the spinoff series - Metal Gear Rising: Revengeance - was developed by Platinum Games and released in February 2013 (and on PC the following year). We'll keep you updated if and when more information becomes available.