I don't think they are supply constrained now. They have had two rounds of incentive programs at the end of 2015 to boost Model S sales. That indicates the Model S market may be getting close to topped out. The market for $100K cars is very limited and Tesla has come close to saturating it. They would get a few more sales if they could defeat the bans in places like Michigan, but it would probably cost more to fight that battle than they would make if they won at this point. When they have a mass market car, that's a different situation.
The limitation they will be hitting soon is their production capacity. They added a second production line for the Model X, though both lines can make either car. Each line has a theoretical max capacity of about 50,000 cars a year and they pretty much hit that in 2015. Once Model X production hits its stride, they will be building 100,000 cars with both lines maxed out. That will be their peak capacity until they either add a new production line, make some tweaks to the existing lines to increase capacity, or until the Model 3 comes on line and its new production lines.
They do have a final assembly plant in the Netherlands that is assembling parts made in California. This may increase their overall capacity over 100K a year. I'm not sure if that plant is part of the 100K capacity numbers or not.