Valve is so tight lipped about ANYTHING they release it's crazy.
I think part of it is all the abuse they took from not having Half Life 2 ready on time. So, they keep everything bottled up, so there isn't any disappointment/criticism.
It's one of thier biggest flaws ... but it's how they operate.
Even a fairly simple mod like Day of Defeat has no FIRM release date ... and they have no intentions of releasing dates/screenshots/demos of it until it is ready.