It's easy to forget, given that Half-Life 2 Episode 3 never actually surfaced and probably never will, but Valve had plans that actually went beyond it. Half-Life 2 Episode 4 was on the cards for a while, under multiple studios. The first was Junction Point, which was founded by the father of immersive sims, Warren Spector, in 2004. Like so many Half-Life projects, unfortunately, it never saw the light of day.
"My guess is that they expected faster progress than we delivered," he told Jeremy Peel...