I see by your figures that you’re correct, sales of the S are flat. However it seems they are selling more luxury sedans than their competition so flat sales do not mean it’s not high demand.
Do note that their quarterly delivery rates are increasing. Ostensibly from Model 3.
Q2 2015 11,532
Q3 2015 11,603
Q4 2015 17,400
Q1 2016 14,820
Q2 2016 14,370
Q3 2016 24,500
Q4 2016 22,200
Q1 2017 25,000
Q2 2017 22,000
Q3 2017 26,150
Q4 2017 29,870
Q1 2018 29,980
Q2 2018 40,740
https://www.statista.com/statistics/502208/tesla-quarterly-v...