More than that. If Model S & X sales = 200,000 and Model 3 = 100,000 cars, with previous cumulative total cars sold = 250,000, the Tesla will double the number of cars on the road in 2017 compared to 2012-2016. They'll likely have to add 50% to the network each year.
Worldwide
2012 - 10
2013 - 54
2014 - 191 so far, 250 projected
2015 - 375?
2016 - 550
Total to start 2017 = 1239
You're assuming that if you double the number of cars, you need double the number of superchargers. This is not necessarily the case. As the numbers start getting larger, the probability of blocking becomes less. In other words, a supercharger with 8 stalls can accommodate more than double the number of cars one with 4 stalls can accommodate without a chance of someone having to wait for a spot. In fact, it can actually accommodate almost 4 times as much traffic. I think many supercharger locations today are still largely underutilized. The biggest issue is one of reach as opposed to capacity. I know there are exceptions to this in some very heavily used locations in CA, but for the most part, the network is underutilized. That said, I wonder what they are targeting as their "busy hour". Popular holidays when people take road trips are probably what they need to plan for.