I also wonder how differnt Dragon Con attendees can be, if Anne McCaffrey can be a guest there - implying book readers attending.

Not really that different, in my opinion, although I'm a Wild-Eyed Lunatic Radical to some of the more conservative elements of "traditional" SF fandom. But OTOH, what you see with D*C is that while they include many authors in their guest list, the convention is so large that the percentage of readers doesn't have to be that large for the absolute number to be large. With a more literary-oriented (note that I didn't say exclusively literary-oriented, despite what some people would prefer) convention like Worldcon, you've got a higher percentage of readers.

I think D*C is what Worldcon would tend to become if Worldcon was anchored in one spot and pursued a growth strategy.