>>149906703Portal is part of the Half-Life universe so the story will continue in Half-Life 3.
HL2 EP3 will end with Gordon going into a helicopter, and because helicopters always get shot down, exactly that will happen and Gordon crash lands on the field where Chell exited the Aperture facility at the end of P2.
HL3 will feature a co op mode where one is gordon and other is chell