If R1S deliveries start in "fall" like they've said, then they must have 2 production lines.
There are 2 total production lines: 1 for the R1 vehicles and 1 for the Amazon vans. The R1T and R1S will come off the same assembly line in the beginning. They will eventually add another assembly line, but I'm not sure they'll need it for a while. They have said full production capacity for the R1 line is a vehicle every 4 minutes -- there are 15 stations each setup to be 4 minutes or less of assembly work. They could easily get to >1k vehicles per week at that rate. That's pretty solid production for such an expensive vehicle.There are 3 production lines.
Once they have cheaper models, they will need more lines, but those could very well be in the new factory at that point.