The review was written while the game was still in development.
It seems to me that HL3 will still see the light of day. There is a possibility that the developers are simply waiting for the very moment when the world is ready. To blow everyone's minds. Or they'll suddenly release it with some incredibly anticipated game in the background to outshine it. I don’t know for sure yet, there are too many guesses. But I wouldn’t refuse to keep quiet for Gordon for one more part.