I can't wait for HL2 to come out. I reckon it could be great for the MIGC.
As well as Counter-Strike Source, Valve have also confirmed that the long-lost Team Fortress 2 is still in heavy development for Source - although they didn't say whether or not it was a standalone product.
They've also hinted strongly at a Team Fortress Classic Source too (ie: a remake of the current TFC, rather than the whole new game that TF2 is), which would be brilliance.
Add to this the fact that HL2 will come bundled with a totally updated HLDM, that all the HL1 mod makers won't have too much difficulty porting their mods to HL2, and that there's already dozens of awesome looking mods for it in development, I can see HL2 having the same massive impact on the gaming scene that HL1 had.
Oh, and just in case anyone missed it it, Half-Life 2 can now be downloaded from Steam in preparation for the very close release. It cannot be played yet, but if you're planning to purchase it through Steam it's probably better to get it now since the servers will be too busy to download it around the launch.