I will say that I expected every installment would end without resolution, forever and ever… there was some rumor going around that Ep3 or HL3 would end Gordon Freeman’s story, and I don’t think that was accurate.
That’s not to say the series was meant to end as abruptly as it did. After the sudden ending of the last game in the series, Half-Life 2: Episode Two, Valve had promised to release a third episode that would wrap up that particular story arc. That, unfortunately, never came to be, despite Laidlaw saying he had plenty of ideas for Episode 3:
I honestly don’t know if anyone else shared this goal, but it seemed important to me to give ultimate freedom to whoever inherited the series, with my own personal set of loose ends tied up to my satisfaction.
If the series really was meant to keep going forever and ever without a proper resolution, then perhaps its best it stopped where it did before everyone got clamoring for when the Half-Life would come.