At the 2016 annual Tesla Motor conference call, Elon Musk and Tesla Motors plans to advance the Model 3 build plan substantially. Tesla is aiming to get to the half million unit per year run rate in 2018 instead of 2020. This is based off of the tremendous amount of interest received for the Model 3, which I think is actually a fraction of the ultimate demand once people fully understand what the car’s capable of and are able to do a test drive.
Tesla would then plan to have around a 1 million car per year production rate in 2020.
In 2015, BMW had a production volume of about 2.25 million.
In 2020, Tesla would be nearing the production volume of Mazda and Mitsubishi.
SOURCES- Tesla Motors, Seeking Alpha, Wikipedia