should put a spoiler warning on this thread for people who havent yet played episode 2.
in brief: in episode 3 you're heading to the arctic with alyx to hopefully locate the Borealis, a ship used by aperture science that according to reports has been stranded in the arctic for some time. You hope to find a weapon on the ship that could potentially turn the tide of the war in favour of the rebels and win the war against the combine. The CEO of valve has played down straight the possiblity of using protal technology in open gameplay in half life. Portal is a game in its own right and shouldnt be looked at as a 'test'. So i doubt you will get hold of the portal gun in episode 3, but somewhere along the line you will cross paths with things that will be familiar from portal. (It'd be good if you crossed paths with glados from portal on your trip with alyx
) With black mesa destroyed, aperture science were working in competition with black mesa in portal technology (black mesa's experiment went wrong and opened a portal to the combine world. hence why everything went wrong) so you hope to find aperture science's technology and use it to fight the combine.
episode three will be in the snow, and i cant wait