I have to differ slightly from what Andy said.
Regarding the Crusaders. Yes, there is a big difference between the two ranges but the popularity of that range has drawn off the house that K & C World War II built. You would have thought that there would be a slightly heightened interest in the special figures. I think what you have is many K & C collectors getting interested in this range because it is K & C, not necessarily because it is a medieval theme. If it draws more people in, then prices may go up. I think the same thing may happen with WWI. I don't collect WWI from other companies and because I think K & C is superior in quality, sculpting, etc. to all other companies I will collect it. Otherwise, I wouldn't buy WWI. These ranges draw in the K & C collector but I'm not sure how many of the non-K & C collector.
Regarding new blood in the hobby, I agree that new people are coming in but we need to distinguish between those who come in and want to buy everything K & C has ever made (Bill Sager, Larry and me, for example) as opposed to those who just want the newer sculpts or can't afford the older stuff. I'm sure the latter will keep sales moving forward but I'm not sure about the former. I believe that is the point Gideon, George and me were probably trying to make.