I just thought of a serious way that Portal 3 could happen and still have Chell as the main character. If you have ever seen the Truman Show you will know why I might come to this idea.
When Chell is kicked out of Aperture at the end of Portal 2, she ends up in the outside…
Honestly it’s not deadly at all: Portal 2 Ending to Portal 3 Beginning?
Yutaki's Tumblr 