Here is an example of the production time sheet of a "fast lane" car. Build start has been April 3rd, pick up date has been April 29th - adds up to soem 3 weeks bare build time (mind there has been the easter holdays in between!).
So: if the´re doing it really "serious" - 3 weeks seems a quite ambitious aim!
It doesn´t matter how fast it becomes, but how it becomes fast. 2015 Roadster 3.7