Did they not have some vague ideas as to where episode 3 was going to go when they designed the cliffhanger for episode 2? Or did they just write themselves into a corner and they haven't come up with anything to follow it? That's a pretty amateurish approach to storytelling if so.
And their clear lack of inspiration didn't stop them releasing HL2: episode 1 or LFD2.
They didn't even know what they were doing with Half-Life 2.
Look at the plot beats:
ACT I: To learn more about this new world, get to Eli in Black Mesa East! He's the carrot who is promised to explain why Gordon has shown up. The game actually
never explains this, so it's just assumed the player was there to fight the Combine. You might say "oh, that's self-evident." On the contrary--the lack of any clearly stated motive indicates a deeply-rooted narrative issue.
ACT II: Eli has been kidnapped and you are stuck in Zombietown! Get out of Zombietown and... rescue Eli in Nova Prospekt. At this stage, whatever non-stated reason for showing up in the world the player had is thrown out the window. Eli is the only objective now.
ACT III: Eli has been kidnapped
again, having been taken to the Citadel! Fight your way through the city to get to Eli!
(Episode 1)
ACT I: The Citadel's going to explode! Eli says to delay it, then catch up with him. You stop the Citadel from exploding.
ACT II: Get out of town and catch up with Eli!
(Episode 2)
ACT I: Eli's daughter is hurt! Save her!
ACT II: Get to Eli!
ACT III: Eli will explain everything, but first, there's an attack going on, and you've got to stop it!
Oh wait, Eli dies.
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Consider that.
There is literally no reason for Gordon to be in this world. Every event that's happened has been something that has pulled Gordon away from whatever that objective was.
Consider the motive of Half-Life:
ACT I: Survive.
ACT II: Now the military is going to kill you. Get to Lambda and stop this!
ACT III: Welcome to Xen. Kill the guy responsible.
These motives are all coherent. Unlike Half-Life 2, they are all directly related to player self-interest, rather than some sort of assumed empathy (there is no reason to care for Eli beyond the game saying "he resists the bad guys! You should care!").
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See, Half-Life 2 never really does motive right (I wrote a thread talking about this thing earlier; if you're even remotely interested, check it out). It never provides compelling reasons to move from point A to point B. It never even tells you
why you have shown up, beyond an ambiguous "you should probably stop the Combine." That seems like the obvious goal, but nothing you do really works towards that. Even vague hints at the nature of how you stop them are nothing more than just that. Vague.
The joke could be that Half-Life 2: Episode 3 can't be made because Eli is dead.
But in truth, I think it's because Valve's development style doesn't really work for huge, overarching narratives. It works best if you want to make
one focused, single-player game. Storytelling requires a writer's distinctive voice. Collaborative narrative efforts rarely work, but that's the very
core of Valve's development style.
There's no sense of planning or focus, just a bunch of people doing things that sound good at the time.
The game's narrative follows a course that indicates people were thinking bit by bit. "Okay, this bit of the level happens, now what do we do?" "Oh, hey, I think we should have a trap town there, so let's put it in somehow." It's not cohesive in any way. It's all thrown together, explained as logically as it can. They did well with what they did, but in the end, it's a game where nearly every major story beat is centered around getting to Eli Vance or protecting him (Citadel explosion, attack on the missile). The game seems to have no central narrative motive or theme beyond this, other than possibly "stop the Combine," which it almost entirely avoids directly (ex: you don't go to the Citadel to stop the Combine, you go to rescue Eli). They haven't planned this out--there's no indication that they're working towards some conclusion. They're making it up as they go along, doing what sounds good at the time.
Take, for instance, Portal/Half-Life 2: Episode 2 and the way they connect. Someone, at Valve, probably put the Black Mesa thing into Half-Life 2 as a joke. It's a hilarious joke for those familiar with Valve's history, but then someone else thought it would be a good idea to make this connection canon, which is where Episode 2 comes in. You can put Black Mesa in Portal as a joke, because it's nothing more than that--a joke. In Half-Life 2, it would have to be a big piece of the fiction, but
everything about Aperture Science is so jokey and silly that it just wouldn't fit. There can be no serious version of Aperture Science.
Valve wrote themselves into a corner with that mistake, and that's probably costing them quite a bit.
From a purely narrative perspective, Half-Life 2 and its sequels seem to have no cohesive vision, no reason for being, no sense of
purpose. They're just heavily atmospheric games with a gravity gun.