This is Yoteslayer's Video, not mine. Sorry if it has already been posted.
So this either means that area 51 isn't on Earth or we didn't actually blow up earth. This might be the lead that the zombie story continues on.
It could be on earth but Treyach failed on the sky when you teleport back to earth after doing the easter egg, but even when you do the easter egg only the bottom half of the earth is blown up so zombies in the arctic or Russia.
We have to wait and see what happens in 2012 with Treyachs next game