On December the 5th, Konami put up a teaser page on their Japanese site.
The site only had this image:
From the few sites I've checked out and the YouTube videos analyzing it, it seems to be the popular thought that this shows a Metal Gear is heading to the 360. People have said the stand-by symbol could be a sign, even though it's a pretty universal symbol. From what I've read, no one seems to notice that the end symbol has an exclamation where it should just be a vertical line. I'm not sure if that's a clue or even important.
Other people are reading it as the i represents either the Wii or the DSi and the ! symbol meaning a Metal Gear game and the power button meaning "Go".
A few have even said it could mean a Metal Gear for the iPod or maybe a new Metal Gear Ac!d game.
I'm not sure, myself. It says "next" so it wont be a port, will it? Whatever it is, it'll probably be something new.