Few. After the ending of Portal 2, I doubt there would be a problem leading to Chell's Re-Entrance into Aperature. Since Glados was erased, it would make for a good storyline, but would re-hash Portal 1. Portal is still a good game, and it would always be dumb to put a money making game to rest. In the end, it's their choice.
1 in 3
1 out of 3
They're making a Portal 3, so yes.
Portal Portal
Portal 2
The chances of being born a twin is 1/33
Nothing has been announced as of May 22, 2011. But there is still one unfinished story chell's past I don't know if there is going to be a portal 3 but I sure hope so :) SPOILERS!!! I hope there is, but Chell's life ended nicely, her leaving. If valve really wanted a portal 3, the field chell went to could be fake, a test chamber... Then there is ratman, Atlas and P-body, and at the end of the co-op coarse, there were alll thoes test subjects.. Please valve!!! PORTAL 3
hepatic artery, portal vein, and common bile
Late 2013, maybe. ;)
Urm... you just buy Portal 2 from Steam and then play it...
George's chances are 1 in 3. His sister's chances are 1 in 5. The two probabilities are unrelated, nor is the fact that they are twins.
the next valve game coming is the portal 3 half life 3 thanks for asking and have fun on the game bye for now