Never mind HL2 Episode 3 becoming a new Duke Nukem Forever... I'm not here to talk about that.
I'm here to talk about the naming of the trilogy. I have never understood it.
After the success of Half-Life 2, Valve started developing a direct continuation to it, in the form of smaller games in an "episodic" format. The original intention was that instead of spending two or three years to make one big game, they would publish smaller games at a faster pace. Of course we all know what happened to those plans (while Episode 1 was slightly delayed, it was more or less in par with the plans; Episode 2 was way, way delayed; but neither compares to the ridiculous delay with the third one) but as said, I'm not here to talk about the delays.
From almost the very beginning Valve announced that when the three episodes got published, they would effectively constitute Half-Life 3. So it puzzles me to no end why exactly they are named "Half-Life 2 Episode 1" etc. when they should be quite obviously called "Half-Life 3 Episode 1" etc. They make up HL3, so it would only make sense to call them that. The first game is the "first episode" of HL3, and so on, so why not name it as it is?
Naming them "Half-Life 2 Episode X" only caused confusion. In fact, even today it still causes some confusion among many people who are not so hardcore players (and might not have played the episodes.) They do not really know what the name implies. It sounds like some kind of remake, or even prequel, to Half-Life 2. In fact, the naming would really make a lot more sense if they were prequels.
That naming scheme makes absolutely no sense for a direct continuation to the story.