While it pales in comparison to Metal Gear Solid: Ground Zeroes, especially because no footage or solid (okay, I'll cool it with the solid puns) information was shown, a Metal Gear Solid movie was also announced on stage at the Metal Gear 25th Anniversary Event in Japan.
It's being produced by Avi Arad in collaboration with Konami and Kojima Productions for Columbia Pictures.
Arad's produced a number of films based on Marvel Comic characters—most recently The Amazing Spider-Man—and is heading the projects for many video game to film adaptations such as the Uncharted and Mass Effect movie adaptations.
Arad has also produced a Bratz movie... sooooo...
Still, it sounds promising enough, especially if Kojima and Konami remain involved in the project. Hopefully we'll hear more on the subject soon enough.