Metal Gear Solid: Rising to use all new engine
We all know that Metal Gear Solid 4 has some of the best graphics to date but today game developers have announced that the game will use a brand new engine, and that they will not be using the engine that they did in Metal Gear Solid 4: Guns of the Patriots. They claim that the engine is built from the ground up to provide the best graphics possible.
"We're redoing the engine from scratch, and it's going to look amazing," Said Sean Eyestone on behalf of Hideo Kojima.
From this we know that the team is serious about the the game and it isn't a quick add on to the series.
Source: http://au.ps3.ign.com/articles/994/994748p1.html