We'd venture a guess that one of those twists has to do with wherever the portal featured in the cover art leads to -- a misty, jungle setting where some sort of seemingly derelict facility stands, overrun with vines. The flip-side of the cover is (cleverly) a view back through this portal into a familiar Aperture Science setting. Finally, the single cover line mentions "the people who are still alive," a potential hint at a reason for venturing into the new setting in the first place.
The issue should be hitting subscribers' mailboxes soon. Check out the full covers after the break.
Source -- Game Informer
Source -- Valve