SF Signal has published one of their "Mind Melds" about What Worldcon and Comic-Con can learn from each other. Like Cheryl says, I think anyone proposing that Worldcon should settle down in one place so it can Get Big has missed the point. The Olympics have had similar arguments. It's very inefficient for the Olympics to be in a different place every four years; it would be much better if they picked one place and built a permanent Olympic facility. (Greece would be traditional, but I bet Sydney would work out better and be more comfortable.) But part of the point of moving around is to bring the event closer to different people. Comic-Con may be wonderful, but it's always in San Diego, and if you live in (say) Glasgow, it's always going to cost you a fortune to attend, whereas a Worldcon can be expected to sometimes come within relatively easy striking distance.
But what do I know? The last time I attended Comic-Con, it was merely 30,000 people.
That doesn't mean that I think Worldcon is Just Right. It isn't. If we could get it up to or beyond its historical peak attendance of about 8,000, it would work better as a convention without destroying the management paradigm Fandom developed for running it. And it would cost less per person and we could charge less for membership, too -- on the order of $100 less at the door than we currently charge.