Well, to begin with, regarding the GDC 2004, it looks like Half-Life 2 with the Source Engine showed up at this year's GDC. Here's a snoop from the IGN report:

"While the demonstration was aimed at the game development community and it only included video from the E3 demonstration, we did get to see the technology behind the engine in a little more detail.
The demonstration was split into several parts, highlighting the renderer, physics, AI, character expression/emotion, sound and multiplayer features of the Source engine, as well as highlighting some of the built-in world creation tools available to developers."


And a snoop from the Gamespy report:

"The first thing you notice is simply how detailed the models in Half-Life 2 really are. Only when the editor is zoomed in all the way can you start to see the edges of the polygons -- closer than you'd ever have an excuse to go in-game. The skin is immensely lifelike: it's got blemishes and zits."
Sounds good!

Also, the SoftImage&#124XSI EXP for Half-Life 2 has been released. You can download it here. It's a 161.9 MB sized download, so beware dial-up users!

Here's some information in the readme about the SoftImage&#124XSI EXP for Half-Life 2: "The SoftImage&#124XSI EXP is a complete version of SOFTIMAGE&#124XSI that lets you output Half-Life 2 characters, props and worlds. The XSI EXP for Half-Life 2 has all the tools you need to make your very own artwork for the world's coolest game, from polygon modeling and lightning fast subdivision surfaces, to nonlinear animation mixing and interactive simulation and rendering."

Sounds great! But then again, it's no promised Half-Life 2 SDK, but at least the next good thing, and good enough!

At last now, Half-Life 3(yes, hence I said 3en confirmed by Gabe Newell, and is already underway in developement!! It is strange that Gabe Newell refuses to deliver any more information about Half-Life 2 that is still waiting on it's release date and will offer information about Half-Life 3...but so far we only know that in Half-Life 3 that the conversion of Alyx Vance from a NPC to a fully playable character. Alyx is Gordon Freeman's female sidekick in H-L 2. The revelations did not stop there however and Mr. Newell also promised plenty of alien-based revelations. And you can still expect to see Half-Life 2 at this year's E3 in May and that it still targets a Summer 2004 release date!