Valve’s Chet Faliszek has recently told videogamer that Portal 2 is going to have two endings each featuring “something special”.
Valve was so impressed by the reception of the first Portal ending they decided they had to one-up the original game. While Portal had only a single player ending with the addition of co-op Valve is adding an entirely new ending.
Faliszek also mentioned the game’s difficulty stating that Portal 2 would have puzzles that make you think but would never do so difficult that they made you quit. Valve wants everyone to see both endings.Portal 2 to have two endings,