Just like domestic anime distributors had to "evolve" through the various economic changes, conventions had to "evolve" too. Luckily, the evolution took place about 2-3 years ago and everyone is just now getting settled.
A lot more is involved in getting guests than only what a convention can afford, a lot of it is also who is available and what support the domestic distributors can give. Distributors are minimizing their marketing spends and that has affected most guest attendance, leaving more of the costs up to the conventions.
The good news however, is that anime fandom has been fairly consistent for the last 10 years or so. I think that this is primarily due to fans from the 80s and 90s exposing the medium to younger audiences. We're finally at a place where those younger audiences are now becoming adults and they are still enjoying anime because of the wealth of genres and story-lines that still captivate them (at least that's what Funimation/Navarre, Bandai, and Viz Media hope for).
I really thought anime distributors and conventions would be dead around 2006-2007. With piracy running rampant, people stopped buying discs. As a product analyst at Hollywood Video, it was a constant fight to make sure even anime movies were represented in our stores due to low sales/rentals (one of the incorrect thoughts was that due to the numerous DVD volumes, people weren't interested in renting them). Once Funimation and Viz Media started cracking down on piracy by beating the pirates to the internet with legal versions of shows, I knew that as long as the fans kept patronizing them, the industry could survive.
I think it's a good start that Kumoricon is now allowing non-anime fandom to have a strong presence at the convention and maybe we'll evolve into more of a "media fandom" convention in the future. We'll see!
