Glados is coming back

Portal 2 takes place hundreds of years after the first game. GLaDOS remains alive, as well as Portal's protagonist, Chell; retroactively patched, the ending for the first game shows Chell being dragged away by a robotic voice, where she is put in stasis over the years.[3] The game will take place in the Aperture Science Labs, untouched by human hands but overrun by decay and nature.[3] The player will interact with many of the numerous personality cores, seen in the post-credits scene from Portal, which have become active in the intervening years, using the automated systems of Aperture Science to create their own microcosms within the facility.[3] The cores themselves are unable to move save through overhead rail systems. Chell is awoken by one of these, Wheatley, who has become concerned for the state of decay and seeks to correct it. Wheatley acts as the player's guide during the tutorial and initial stages. Soon, the two are introduced to GLaDOS, who is quick to accuse Chell of murdering her years ago.[3]

Two new characters will be introduced for the two player cooperative mode, which will have its own unique plot and setting.[4] These two yet-named characters include a modified turret gun and a personality core; both units are bipedal and equipped with their own portal guns.[3] Thought once part of the networked facility, they have become separate entities, and are treated to similar abuse by GLaDOS as Chell is, being put through a series of complicated test chambers.

here you can read more about portal 2[en.wikipedia.org]