Maybe it's wrong, but maybe it's not.
I wasn't inventing the "H-L3 isn't worked on due to MOCAP issues" part, you know. It's John Patrick Lowrie (voice actor) who said that. Apparently, he said (as far as he knows) Valve wasn't/isn't working on H-L3, period (for now) due to technologies in the MOCAP industry not meeting their expectations, or whatever it is they don't like about the latest MOCAP stuff around. Do I think that Valve went bunkers if that's true? Yes. Simply because to me H-L2's animations were more than enough to convey, portray and express believable-enough emotions without the need of cut-scenes or quick time events to tell a story. They managed to do it with H-L2, all they had to do for H-L3 was to increase polygons count and textures resolution and they'd still have sold millions.
Do I know for sure what Valve is up to? Of course not I'm just Mr. Joe everyone without much evidence other than what John Patrick Lowrie said. But am I ready to immediately disbelieve what he said? No. That's simply because... well, you know, Episode Two was released in 2007, we're in 2013 and the next big Valve project appears to be L4D3. I certainly think that something isn't right concerning H-L3, even if the true reason isn't the MOCAP stuff that supposedly bugs them that much. It could be something else entirely, maybe they're waiting to see if they could release it for Linux as well, or maybe they're developing it for the XBOX One and/or PS4 and want a multi-platforms release. I don't know what's going on but what I do know right now is that H-L3 is freaking overdue and should have been released at least two years ago by now.
If, however, they do announce Half-Life 3, I'll probably be the first to come back in this thread and kick my own ass for apparently being naive (albeit with a reason that is called "waiting since 2007 for a damn sequel").