Mark CMG
Creative Mountain Games
While I'm another over-40 4e fan, I do find myself gaming with a younger and less homogeneously-longtime-D&Der crowd under 4e than I did under 3e. So, I can see where the impression comes from. 3.5/Pathfinder games I see happening at the FLGS (one each) have a more uniformly 30+ crowd (even a couple over 60), while the 4e games have a lot more 20-somethings and a sprinkling of actual kids (but still are about half gamers who, like me, started playing in the previous millennium).
One phenomenon I find heartening is that you see families gaming. You'll have a dad who gamed back in the day, and he brings his kids to play.
The longest running group game at my FLGS (in business for thirty years and the group about that old, as a group) currently plays PF and includes gamers from 20 to 50 (approx), including a father and his two late teen/young-20s sons. Of the 4E games I regularly see, one is a young 30s DM with players from mid-teens to early 40s while another 4E game has mostly 30-somethings. I think the Encounters games tend to skew younger, from what I have seen, and my own weekly game which switches between many systems includes early-20s players (most of the players are in this age segment) but with some early-30s and a couple of players in their late 40s/early 50s. There's another 3.5/PF group (they seem to switch off) that is mostly 30-somethings. This is just on two of the seven days their nine game tables are open or scheduled for games. There are also a lot of wargamers, FoW, WH, Hordes, etc. plus clixers using those tables, and a handful of nights when it is almost all boardgamers and a handful when there is a lot of card games.