Okay, so the whole Borealus thing. Half Life 2 e 3 will probably have the portal gun. The whole point of the borealus to begin with is that they have Aperture's portal technology alternative onboard -_-;; I dunno; not particularly looking forward to it.
Well it won't necessarily have the portal gun, after all the ship itself has portal technology and it seemed to me that from playing portal the portal gun was still in development at their lab so it seems more likely that the ship itself is a large scale portal device rather then that the portal gun itself is on onboard, just my two cents seeing as how the ship seems to teleport to different places.
EDIT: Oh and also I think the point of the last battle is that you don't have much ammo, your supposed to use the magnuson devices, but yeah gets a little old after all the striders.