Despite the increasingly frequent calls for less frequent General Assemblies, it isn't going to happen. I don't think the usual reason given is correct; that is, that the ministers and "GA junkies" (a detestible term) are too invested in having it as a social affair and a junket. Some ministers surely do, but if given the choice between a GA venue (Quebec City aside, which I loved) and -- well -- a real holiday destination, which would you choose? Plus, there are other conferences, retreats, and study groups to attend where you can catch up with your buds better. (As for the GAJs, I can only guess, but I imagine with the growing number of GA attendees, the GAJ power ratio is diminishing. That's assuming they're not the stuff of legend. I mean: do you know any?)
The real reason is that's where the power is. Not that there's much formal power, but all there is rests there. The Association is a creature of the congregations, and the districts are the creatures of the Association. They are autonomous (per the UUA bylaws) but clearly not autocephalus. A congregation may unilateraly leave the Association, but I daresay a district cannot.
More to the point, a congregation joins the UUA and from where it is becomes a member of a district. The membership of a handful of congregations that are members of districts but not the UUA hardly alters the "boomerang" relationship, where Boston is the first point of contact for many -- perhaps most -- UUA functions. I suspect this is a question of critical mass more than polity.
But the point is until -- if ever -- the districts are the first point of organization contact, with power, budgets, and mandates to match, then the UUA and the General Assembly will have a cachet as the "place to be," even at great cost and distance.
Out of necessity, this would mean many fewer districts -- perhaps six or seven instead of the current twenty -- and I don't see that happening soon.