Hideo Kojima talked a little bit about Metal Gear Rising Revengeance during the PAX 2012 panel.
‘Rising’ in the title refers to raising the Raiden character, bringing him up to the stage. It also refers to ‘rising sun’ and the samurai theme. ‘Revengeance’ refers to ‘revenge’ the team takes on the previous (failed) build with this new version. Players will be able to take out their frustrations of life with this game, by cutting everything into little pieces.
Kojima is not a huge fan of spin-offs, but if Rising works he would like to work with Platinum again and make a sequel.