UK magazine PSM3 says that Hideo Kojima is going to announce more than one game at this year's Electronic Entertainment Expo. They say:
MGS maestro Hideo Kojima's got some big announcements for E3 in June: one a quasi-logical step for an existing game, the other...
So, Metal Gear Solid 5? Finally? The timing would be right, I'd say. But as G4 says, why would they announce two games at once? Wouldn't an MGS5 announce overshadow any other announcement.
The only other one that would hold up in my mind is a Zone of the Enders announcement. In that case I'll sh*t my pants with excitement. Regardless of where you are, you will hear me scream in joy from Los Angeles. He did say that a third game was coming. E3 is just around the corner, so we'll know soon enough.