The problem, however, is that one line rate will be maxed out at 50-60K units/year, and this rate will be fully utilized for MS by the end of this year. TM will need second line by end of the year to tune production of the MX. They are not talking about this yet, because it is not a 100% certainty at this point, but that what I believe the plan is. If you remember, they for a long time were talking about 800 cars/week by the end of this year, before switching to 1000 cars/week by the end of this year. Based on all circumstantial evidence that I posted numerous times before, including the Panasonic data, I expect this 1000 cars/week by end of this year to be updated again to 1200 cars/week by the end of this year.
I agree that the production line will be producing 1000+ Model S cars/week by the end of the year. I really would like to believe they can and will do 1200 cars/week by the end of the year, and they could possibly have the batteries for it, but I don't know. I think it's possibly it could be an internal aspirational goal for Tesla, but we know publicly that they've committed to 1000 cars/week and 35k cars delivered as guidance. And if I had to choose one, I'd go with guidance as my expectation.
I have to admit though, the Tesla job fair they had a couple months had me confused. If Tesla is ramping just to 1000 cars/week by year-end then do they really need to be recruiting so many people? I don't know. But on the realistic side of things, ramping to 1000 cars/week will be quite an achievement and while we all hope they'll do more, I think it's probably more hope right now than solid.
Regarding Tesla needing a second line by end of year to test/tune for Model X, I'm not sure if I agree with you on this. Can't they can test/tune for the Model X during a 3rd graveyard shift?