As of yesterday, Metal Gear Rising: Revengeance can be purchased as a digital download on Xbox Games on Demand.
“The Games on Demand version supports English, French, Italian, German, Spanish, Portuguese, Japanese. Download the manual for this game by locating the game on http://marketplace.xbox.com and selecting “See Game Manual”. “
The game costs $49.99 / €64.99 and is 7.43 GB in size. For the full description, or to purchase the game, click here to visit the (US) Xbox Live Marketplace.
Update: Konami confirmed via Twitter that the game will come with the Gray Fox skin and Fox Blade.