GamePro got the opportunity to talk to the Hideo Kojima at great length about his upcoming Metal Gear Solid 4: Guns of the Patriots game. He doesn't reveal anything new, but does hint and allude to several interesting things. He starts off by covering the settings, which does start in the Middle East, and is influenced by current events, but he stresses that it's a global game full of traveling from one country to another - more like an "espionage on the battlefield" World War III game. The enemies should act according to their surrounding atmosphere - when things are calm they might just hide and fight back, but when already panicked they'll run away in fear. Snake himself has been aged and is not as bright as he was in previous games, but Hideo didn't want to put the stress on the players, and mentions that Snake wears a muscle suit to keep up to his old ways.
Kojima won't say whether the game is linear or non-linear, but he does mention some interesting things about weapons and countries. He won't say whether or not mechs will show up, but he says there's more gun modification than ever before, and won't say how the player received the special guns. He does say that gameplay will let you take sides with a country of your choosing and pick which other country to target, allowing for backstabbing. The better your side does the further you can go faster through the game. He makes it seem like weapons will pave the course of the game from one country to another, so it wouldn't be surprising if the "Guns of the Patriots" game revolves around corrupt arms deals between nations.
He also mentioned that making it for the PS3 was difficult, but said PS2 wasn't easy either. Along with that, he said he wants rumble feature back, and actually isn't excited about 1080p gaming. After MGS4 he plans to not only get involved with the Wii and possibly Xbox 360, but also PC gaming. His game team isn't a big fan of going down the path but he mentions the desire for making a worldwide game.
It'll still be a while before the game comes out this year, so for more reading on Metal Gear Solid 4, you can read the full GamePro interview here.