All things considered, I think Tesla's biggest downfall will be Tesla itself.
Heavy duty price tag, high priced replacement batteries, short charge span, (relative), should be enough to discourage most.
To me the car is a contradiction. Here is an electric car that performs, but only for a short time, and is to high priced to be economical, which afterall isn't that what the electric part is all about?
I think the concept of an all electric car is great, but untill such time as a long lasting power source is available, it would best be handled as a design excercise as opposed to a marketable product.
Just my humble opinion.