The lights are on
It would be really disappointing if the protagonist wasn't Chell. Portal 1's length was perfect for it's story. The environment was all the same until you get to where "we pretended we were going to murder you" And the change afterward helped it stay fresh and fun. It is possible that it isn't a typical full length game, and if it isn't valve *probably* won't charge 60 bucks for it. Hopefully it is a more full length game though, with a good long campaign, and then plenty of challenge maps to play with. Personally i hope there aren't any guns, i feel like they would spoil the puzzle-ness of the game.