I think not doing HL3 was the right move from the business standpoint. The expectations of the HL fans got so high that anything short of another milestone of PC gaming history would damage them. It is hard to beat yourself, when the last success was so big. Much smarter to put the effort into several other directions.
Doing half life 2, then switching to episodic content so you can get things moving faster, then taking forever to release 2 episodes, then sitting around for a decade with an unresolved cliffhanger is ridiculous.
I don't buy your reasoning either. Right business move because DotA 2 and their Hats! are a cash cow business, sure.
They're waiting for VR. Half-Life 2 already spans everything cool you could conceivably do with a 'post-quake 2' shooter. Team Fotress 2, Counter-Strike: Global Offensive, and Dota 2 cover all the neat online matchmaking, micro-transaction, user-created content stuff.
They don't want to make Half-Life 3, the expansion to Half-Life 2. They want to make something new. They created something new with Portal, which required them to hone their ability to introduce players to an entirely new game mechanic, but now they have to wait for VR to put it all together.
