Unless everyone has a Model 3/Y or Raven or newer Model S/X is plugging in at 5% and unplugging at 60%, it is highly unlikely that there will be any significant throttling. In reality, there's always a stall or two open and people charging to 80-90% so some stalls are significantly underutilized.I think you're severely under-estimating apartment dwellers in the area using this Supercharger (like me).
I go charge when I hit <20% (when Sentry Mode turns off), so at that SoC %, I'm pulling 250 kW easily. I think other apt dwellers will be the same, going to the supercharger at low SoC %.
It's not going to suck for anyone, honestly, unless lines start forming. At that point, Tesla would be better off adding more stalls than adding a Megapack or Powerpaks to help supply more peak power.