You guys fail to realize the other things involved.
Time it takes to update the engine to todays standards
Time it takes to update their other games (after all, people were bitching for how long to get achievements for HL2 and EP1 and such)
Time spent on class updates on TF2
Time spent on their other undisclosed new IP.
EP3 can’t be a priority when millions of people demand all these things and more from Valve. Valve simply does what the masses ask, and the masses really ask too much.