Can't you get 2" smurf tube (that blue stuff, whatever it's really called)? I would think that would be sufficient as long as you don't make any sharp bends. Don't know, I've never used HDMI cables. I thought I was making a big improvement just by switching from component to s-video and optical cables.
I've seriously considered building an A/V room with drop (acoustical) tile ceilings just for these reasons. Have 3" conduit coming up inside each wall and have an access panel right above the ceiling line. Single-story houses are easy as long as you can get into the attic, but multi-story homes are a PITA for cabling runs.
If you're building, I'm a big fan of having a closet with an open wall / shelving unit that opens up into the Living / AV room. Put all your components on the shelves and walk into the closet to make all of your connections with no hassles. Also a good place for your telephone system and network to end up. If it looks like a bird's nest, so what! It's in the closet, not like it's going to be seen!
Then have 1 or 2 cables run to the TV.
Not a pro - just installed enough systems and run enough cable to have a big wish list.