Correct me if I'm wrong, but Portal was originally an experiment related to Half-Life. Notice how the Portal Gun looks similar to the Gravity Gun? Portal was just merely a physics test, not a actually game. But once they got really into it, Valve released it as a game.
Oh, and I think that The Combine and Gordon can take care of the aliens just fine.
In Portal (number one) if you look into a certain room during the outskirt levels you can see through the window a conference room with a table and loads of chairs knocked over with a slide show comparing Aperture to Black Mesa. When I saw it, it brought a tear to my eye.
Tora
Didn't you see the ending of the co-op game?
SPOILER ALERT!
Atlas and P-body found a vault filled with HUNDREDS of Humans in sleep pods, ready to be awake. GLaDOS happly starts testing again.