What the heck is a "senior US source"?
You know, those people whose job in life is to keep tabs on EVERYTHING
going on in the US. Therefore, you only have to go to them to find out what's going on in the US. Like the fact that Blizzard's next game is Starcraft 2
and the untitled id game is really called Quest
I'm kidding BTW.
However, one of the following things must have happened here:
1) The article is simply not true. The source is a bored 13 year old child.
2) The article's "source" is that same one that said Half-Life 2
was X-Box bound in October, before the console even launches, and vicariously has its source as a bored 13 year old child
3) The article is really referring to Team Fortress 2
which, while still newsworthy, is entirely different from Half-Life 2
4) Realizing that it is somewhat ludicrious to spend years and millions of dollars on a boxed, stand-alone sequel to a Quake
mod, they've just changed the name to Half-Life 2
and have tacked on a single player component.
5) Half-Life 2
has been in development for some time, Sierra farmed out development of it to another team, kinda like Eidos did with the Tomb Raider
6) The Game's really something like Half-Life: Purple Shift
and will be released as part of the Half-Life: Diamond Pack
Notice how these get more implausible as the list goes on. It's just kinda fun to speculate...