I've gotten all the Episode 2 achievements. I just need to get a couple Team Fortress and those Portal Gold Medal achievements and I'll have em all.
The last released Episode 3 date was Christmas 07, but we all know how Valve is with release dates.
http://developer.valvesoftware.com/wiki/Valve_Time
Valve Time: Christmas 2007
Actual Time: Coincident with the Rapture