Warning: It's all spoiler territory from here on...

The script samples we saw for the Cave Johnson role indicate that the Aperture CEO and "eccentric dead billionaire" is, well, already dead, living on in simulated computer form. He tells an unnamed rookie test subject via loudspeaker that "As of this mornin' yer old buddy Cave has been resurrected inside of a computer. And I never felt better!" acting as this entry's GlaDOS—possibly that prototypical GlaDOS, as theorized earlier—encouraging the player to continue the testing while waxing philosophical about the afterlife.

"I been thinkin," the script reads, "Heck, suspended as I am in this inky purgatorium, I got nothin' to do but think. What if them engineers didn't do me no favors pourin' me into a computer? What if they denied me my final reward?"

No telling if this internal conflict is the catalyst for Johnson "[losing] his grip on humanity as the story progresses" but if things go wonderfully wrong as they did in the first, it would certainly make for a compelling narrative.

Snappy portrait! Cave Johnson, now-dead boss of Aperture (who you'll already know of if you ever accessed the Aperture website and had a look around), is playing such a major role that he's described as the "principle antagonist", it suggest that Portal 2 may (may) be a prequel of sorts. Which would make sense from a story-telling point of view, what with the way Portal 1 ends and all. Also interesting that he's described initially as a "sidekick", implying that you may be playing the part of a fellow executive/Aperture employee this time around, rather than a science experiment with a pair of robot chicken legs.

Course, it could also mean Johnson is already dead in this game, with his consciousness living on as a prototypical GlaDOS, but if we start down that imaginative road we'll never find our way back...

In typical Valve tradition, it won't be Portal with different colours. I think that when you hit something like that, you have two choices: you can quickly replicate it and stick it out there - do the opportunistic thing and cash in on it; or you can do the crazy thing like we did after Half-Life was so successful and go off and try and say, 'Okay, that was revolutionary, so its successor has to be equally as revolutionary.