I agree about saying something about Essentials. It's playable with 4E like pathfinder is with 3E? but I feel like it's really it's own thing in feel and power balance.
Though I'd say it's worth a bullet-point, because the D&D scene isn't bi-polar, OSR makes up a significant portion of "D&D" gamers. Especially with all the 3e/d20 variants like C&C and Hackmaster.
Has anyone ever guessed at numbers? I see internet excitement, but I haven't really seen older editions being played to any significant extent (despite traveling pretty widely across the US).