I doubt Tesla will give up on their U.S. factory, unless the company ever enters dire financial trouble. There have been (and still are) major auto makers with factories in the U.S. It is to their advantage to operate more than one factory if ever there are labor issues, governmental issues, or even natural disasters that could stop production.

I suspect US will be reserved for high end S/X models, with the model 3 likely majorily in China.