A new listing at Amazon seems to have outed the release date for the PC version of Metal Gear Rising: Revengeance.

They have the release set for January 9, 2014 at 10AM (PT). In addition, the system requirements for the game were also revealed.
Minimum:
  • OS: XP or Vista or 7 or 8
  • Processor: Intel Core i5 2400
  • Memory: 2 GB RAM
  • Graphics: Nvidia Geforce GTS 450
  • DirectX: Version 9.0c
  • Hard Drive: 25 GB available space
  • Sound Card: DirectX compatible sound card

Recommended:
  • OS: XP or Vista or 7 or 8
  • Processor: Intel Core i7 3770
  • Memory: 4 GB RAM
  • Graphics: Nvidia Geforce GTX 650
  • DirectX: Version 9.0c
  • Hard Drive: 25 GB available space
  • Sound Card: DirectX compatible sound card