The game was an ambitious side story that more backstory on what happened to Raiden, and how he went from the mild mannered Jack from Metal Gear Solid 2: Sons of Liberty, to the bad ass cyborg capable of dominating squadrons of heavily armed futuristic soldiers. It was to be set several years after the events of Metal Gear Solid 4: Guns of the Patriots, but it was never intended as a direct sequel to the Metal Gear Solid franchise.
The debut trailer promised that Raiden would be able to chop and slice anything from people to the surrounding structures. The developers put such an emphasis on the cutting mechanics that they began to lose what the core of the game should be. It just wasn’t coming together, and Hideo Kojima felt that the game would never be completed. According to a Japanese podcast that Andriasang translated, the developer eventually admitted losing focus, and then decided to kill the game.
Platinum Games then approached Kojima Productions and offered to continue development. The game was half complete at that point, but Platinum decided to rework the story as well as tweak some of the gameplay mechanics. Kojima Productions is still involved, but only to a minor degree. Because of that, Kojima is not considering that an actual Metal Gear Solid game, but part of a different franchise in the same universe—which is likely part of the reason for the name change. It was recently announced that the game would no longer be called Metal Gear Solid: Rising, but rather Metal Gear Rising: Revengeance.
The game debuted a new trailer at the VGAs last Saturday, and is scheduled for a release on PS3 and Xbox 360 in 2012.