this is probably the same reason why valve hasnt released any "new" games in a while.
everybody is expecting only HL3 from them otherwise they'll be disappointed.
I doubt that. People have been waiting for HL3 since HL2, which came out 12 years ago. It's been 9 years since HL2:Ep2.
In that time Valve released Team Fortress 2, Portal 1 and Portal 2, Left 4 Dead 1 & 2, Alien Swarm, Dota 2 and CS:GO.
I know that not all of those are by the same teams, and Valve's last game was released in 2013, but they clearly aren't fazed by the hype for Half Life 3.