The Tesla/Panasonic plan gets cell and battery production back into the same plant. The battery industry has, for a while, had a model where cells were made in one country (usually Japan, Taiwan or S. Korea, or at least with machinery from there) and assembled into device-specific battery packs near where the end device was produced (usually China or the US.) For the Chevy Volt, the cells come frm LG Chem in Korea, and the battery packs are assembled at the Brownstown, MI Battery Assembly plant.
There's no good reason to do it that way now that the era of cheap labor in China is over. As a rule of thumb, labor has to be 4x cheaper to justify offshoring. The coastal provinces in China have reached that level with respect to US/Japan wages.
Done right, this isn't labor-intensive. Brownstown has only 100 workers in a 400,000 square foot plant, and they're doing battery assembly, which is the more labor-intensive part of the operation. Tesla claims to need 6,500 employees for their 10 million square foot plant, but they're probably counting construction-phase employees.