...eh, who cares?
If they were to put them in the game, sure. It probably wouldn't ruin much, besides it's your choice to aim down iron sites. Just don't use them if you don't want to. Though I could understand how it would mess with the "spraying and hectic Half Life gameplay. Which reminds me, Serious Sam 3: BFE will also have iron sites, so let's see how that goes...then again it is looking a bit gray/brown this time around, but they're in Egypt for part of the game we're just wait and see.
The Half life IP can live without ironsites, but if you want them in there I'm more than sure the modding community can fix that. Besides, I think the zoom in function is already pretty good. Though, when a bit closer, it can be a hassle. Like looking through a sniper scope while standing a few feet from someone. You think it would make things better but...eh, not so much. So I could see why someone would want iron sites...especially with certain guns...
In all I honesty though:
Frankly, I'm just hoping for a few more animations, new weapons, and more enemy variety.
Or perhaps give Gordon different levels of zoom.
But hey, what do I know?