For 2010, the population of Black City went beyond 51,000. Other than the B.L.M. permit requirements, are there any limits of growth? Given the recent trajectory of growth, the population of Black Rock City could exceed 100,000 in seven or eight years.
The current city planning concept is brilliant. As the population grows, more perimeter streets (L, M, N, etc) could be added and perhaps starting at "K", you would find 0:15 and 0:45 radial streets to keep the blocks at a manageable scale.
One of the downsides of this population growth would be the arrival and the exodus. Perhaps the Man burns on Friday night and the Temple burns on Saturday night to allow for a larger "exodus window" for the population to return to the default world.