I think most of these guesses are wildly optimistic. Consider:
1. GB has referred to the "re-estimation" of cars by the end of 2012 as 2,500-3,000, not 3,000-3,500. Don't know whether that's produced or delivered.
2. With the shift in delivery windows, it looks like the Sigs will be getting delivered at least through the end of November.
3. While there is no consensus as to the sequencing/numbering of the Rs, it is quite likely that 400-500 Rs will be produced before the Ps get produced.
4. There is some possibility that up to 200 Canadian SSLs and Sigs will be produced before the Ps get produced.
5. Ramping up to 400/week by year end probably means around 1400 cars in December.
On the other side of the equation, the predicted highest production number will be increased by cancellations and deferrals, and by the assumption that only the 85kwh cars will be delivered in 2012.
Taking all this into account, I will be surprised if the highest production number delivered in 2012 exceeds #1,000. Of course, it is just a coincidence that my number is 983.