Well maybe you are correct but then why do they need to hire a story writer then ?
Most games, even if they are very simple in terms of lore, require a writer. Specially in games developed by big companies like Valve.
Games like TF2 do require loads of story writing... have you seen the comics? They have a universe and a lore behind it all. It's insane.
Same applies to DOTA2, afaik. Every champion has its own background story, and that requires a writer to do so!
Erik was only involved in HL2:ep1 and HL2:ep2... the real genius behind HL lore is Marc Laidlaw and the guy is long gone, unfortunately... (he did release a possible storyline for HL2:ep3 here
http://www.marclaidlaw.com/epistle-3/ ).
Erik Wolpaw, like I said previously, is mostly responsible for Portal (which does take place in HL universe).
I wouldn't mind - in fact, I would love - if HL2:ep3 or HL3 was to be released soon, though I wouldn't expect much from this news alone.
Valve is having competition, so to get back to be the king of gaming it needs to produce games again. Don't forget that GabeN said in one of his interviews that the portal/halflife universe is not over yet and there is a future game set within that universe.
Competition? The king of gaming? Lol, they own the most profitable digital game platform in the world. They don't need to make games to earn money or any fancy title. They are dominating the industry with Steam, and they don't even need to make games to promote it anymore. Money always speaks higher in cases like this. It's sad, but it's true.
About GabeN saying that in interviews... how long was that? 4 years? 5 years? The main writer of the series posted a draft of the storyline online because, he, himself, was tired of all the waiting... Something is wrong with HL's development... and that sucks ass.
Now, to feed our emptiness of HL, here's a cool trailer of Black Mesa: Xen that is scheduled to release this year
valve time, we all know how long these guys take to release something...!