GF2 is definitely building modules from cells. The big question is how long they were planning to import cells from Panasonic's Japanese facilities. Being unable to (affordably) import cells from Chinese factories was one of the problems that killed SolarCity's earlier plan to scale the Silevo technology they acquired, and drove them to Panasonic's cell tech instead.

EDIT: I was initially wondering whether Tesla planned to make cells in the US for GF2 at all, or just import them from Japan, but according to this report from last March they already planned to produce cells in the US:

https://www.pv-tech.org/editors-blog/silevo-technology-ditch...

From the article in SEJeff's comment:

>The two companies hope to ramp up production at Gigafactory 2 to reach a capacity of 1 to 2 gigawatts of solar products. They currently have “roughly 500 employees” at the plant and the hiring process is ongoing, according to Tesla.

They're currently building panels from imported cells, but the goal is to make everything in-house.