According to the Model 3 reveal, there are 215 Tesla stores and service centers. I figure 3 minutes per reservation, that's about 1,200 people in front of me every 3 minutes. I was hitting the reserve button in the store after about 15 minutes, so that's as many as 6,000 people in front of me. That's the number I'm going to go with for now, but since I'm a Model S owner, maybe that drops in half or to a third. Maybe even to a quarter of that number if I max out the configuration, but I probably won't.
But I think this kind of fuzzy math is the best we're going to get for now.