Will the ES300h continue to be made in Japan
 

or will Lexus also move the hybrid eventually to the US facility as they have with the ES350?

Doubt it. Only a few Toyota hybrids are assembled outside Japan - the Yaris hybrid in Europe and the Corolla hybrid in China. Lexus still make all their hybrids in Japan. I don't think North American ES300h sales justify the cost of adding a new production line to the Kentucky facility.