That's leaked footage put together by a "fan." The sounds aren't real, and neither is the voice. This "trailer" was put on Youtube in December 2009, it's just more people noticed it once April Fools came, for some reason.
Currently 3D Realms still exists, and the game appears to still be in development (not sure how, perhaps another company decided to help), but for now anything released about Duke Nukem Forever (that isn't coming from 3DRealms itself) is either fake, or a leak.
I'm still waiting. :]