Since HL3 is probably never going to be released, I'd love it if Valve released any script or story notes they had for it. I want to see what would/could have happened.
I find it hard to believe there are not loads of //notes// about it. Maybe not a "final_script.txt" but lots of data spread out over lots of files seems logical to have.
The fact that Half Life 3 isn't released and there is no sign of it is almost certainly not due to some failure to produce it but due to a decision not to.
The problem is that the only "new" thing since HL2 that could take off is VR which isn't quite there yet.
At this point games are to Valve what email is to Google. An important product to be sure but not what they make their money with. Valve makes their money with Steam, their games are side projects.
Steam is popular, the games Valve makes are popular and Valve is popular. HL3 is a massive investment, a huge risk to all of that and for what? If Valve were a games company, the money would be the answer but Valve is the Steam company, that money is not all that much to them.
I thought the Portal demo on the Vive was mindblowing. If they released Half-Life 3 in that form, it would survive the anticipation.
No Man's Sky wasn't a simple case of hype, though. The developer blatantly lied about what was going to be in the release version, including videos and screenshots of content that doesn't exist[1]. The extent of this mismatch between what was advertised and what was delivered is so large that it's being investigated in the UK[2].
[1]https://www.reddit.com/r/Games/comments/4y1h9i/wheres_the_no...
[2]http://arstechnica.com/gaming/2016/09/uk-advertising-board-i...
Anyone can make a complaint with ASA, and they investigate any complaint for which they're the regulator.
They also do not uphold plenty of complaints.
To get a feel for what an ASA ruling is like people can read the archive of rulings here: https://www.asa.org.uk/Rulings/Adjudications.aspx
I think this recent ruling about a city council's campaign to stop people giving money to beggars shows there's some nuance to the rulings: https://www.asa.org.uk/Rulings/Adjudications/2016/9/Nottingh...
tl;dr An ASA investigation means nothing other than someone complained.
Valve isn't developing HL3 because a project of that magnitude requires simply more dedication and conviction than Valve's devs might even have anymore. The company is one of those flat structures where developers work on whatever they have passion for, which means anything they make is gold, but if nobody has passion for it it will never be made. And compared to the work required to make all their games since HL2 - not skill, just raw hours of design and testing - HL3 is way beyond the scope of what Valve has made since then. Portal 2 is the most significant achievement since then, and all it really was was level design and event scripting - there are no real enemies, no AI, and the game length was still quite a bit less than what a full FPS release on par with the old Half Life would expect.
It should be no coincidence the release of Steam ended the Half Life franchise. Once the company had effectively infinite cash the staff could pivot from making complex hard to develop games that would make huge returns to making whatever they wanted - Dota 2 has nothing pay to win, no payments to even play, the only in game transactions are for cosmetics. It is something no other moba, not even Blizzard's, is willing to risk because everyone else is too worried about making sure ends meet from the games revenue.
So I do not believe Valve is incapable of living up to the hype. Even making a game as good as Half Life 2 would be enough. Portal 2 was considered a success despite being inferior to its predecessor because it was still really good. The problem has nothing to do with fear of failure, but a lack of willpower in Valve staff to put millions of hours into making a worthwhile successor to Half Life 2 when they can get similar accolades for much less effort making games in other genres. It is the same reason you so rarely see expansive and good RPGs. They are much more time consuming to make than almost any other genre of game.
I think the point you're making on structure, could also explain the failure of Steam Machines. Something that would require quite a lot of people coordinating not just with others in the company but also with people outside it.
script or story notes they had for it