And here's what I think you are missing: Wiscon is always in Madison. It's just great for the people who travel to it. Worldcon could do something exactly the same: permanently locate itself in one city (I'd pick Anaheim, actually, but you could make a good argument for several others), organize the same way every year by an ongoing group (which BTW would probably cut the attendance price by at least one-third right away and maybe more; economies of scale and not having to pay start-up costs every year), and concentrate on Growth. It would get Big. And it would be come utterly unreachable by most fans.

One of the key things about Worldcon is that it comes to people who can't come to it. Look at all of the Australian fans who are highly unlikely to ever attend a Worldcon outside of Australia. Repeat this for every region that's ever hosted a Worldcon.

You can grow Worldcon and lose many of the things that make it difficult to run, but in doing so you probably make it just another permanent-site convention like DC or ComicCon. It would be just as much the "World" con as the self-named World Steampunk Convention is the "world" gathering of steampunk culture.

But that's probably just dandy for people who can afford to travel a long distance every year or who happen to live within commuting distance of the Permanent Worldcon Site.