Just like the mob, once you've created the Metal Gear franchise, you try to get out but it keeps pulling you back in. That's essentially what Hideo Kojima, creator of the Metal Gear/Metal Gear Solid franchise, told Official Playstation Magazine UK during e3. Initially Metal Gear Solid 2: Sons of Liberty would be the last game he had any involvement with. Therefore he'd never have to deal with clones, origins for origin stories, Metal Gear on Metal Gear battles or even how Snake finally ended his story.
Except, as the last three main Metal Gear titles have proven, things have a way for not going how Kojima wanted. He was forced back on Snake Eater due to creative problems and then Guns of the Patriots because the two creative directors were struggling with how to interpret Kojima's plot (which, frankly, they weren't alone in).
"It’s very hard to come up with the concept of a game and hand it off to other people, as of course they can’t see what’s in my head. They may not be able to understand the concept completely, or the messages that I want to convey and that’s where things went awry in the past as people couldn’t really understand what I wanted."
The unconfirmed rumor about why Kojima came back to Guns is he desperately wanted to prove cinematic storytelling could work on a console. He also wanted to show off the expansive, global storyline with tanker battles and sprawling chases through busy streets, which is why Guns became notorious for its cut scenes. Soon after, Sony came back and gave Konami and Kojima a very low budget, which killed the film adaptation.
Regardless, Kojima's involved again with Metal Gear 5 and Metal Gear Rising: Revengance, along with his upcoming Project Ogre that'll run on the Fox Engine. It's safe to assume Fox Engine will be Next Gen, as the famous office comparison shows. Kojima did reveal the next time he demos Fox, it'll definitely be a bit taken from Project Ogre.