I think cave Johnson from Portal is still alive in the half life 2 & entropy zero 2 universe ever since that one mission in EZ2 where I saw cave Johnson's house in a nice shape, but the problem is........where is he now ? Probably in the borealis? Or hidden in the aperture science facility? Maybe in the team fortress universe?
(Edited)
I believe he's a big robot head somewhere and the rebels were the ones who cleaned his house PS: EZ2 is not canon
It's better if he's dead. He flew too close to the sun.