My reading:
We've known since... a while ago. June? that the number of reservations is 373k.
It's obviously not true that the number has been unchanged since then. The question is how much not true?
We've heard some rumours in the last week or so that the number is over 500k.
We know that expected annual production at Fremont was to be 500k, but that was before all this talk of expanding Fremont and the factory efficiency per unit volume advances found at GF1.
If they could instantly ramp to max-capacity-speed production (they can't, I promise you that) then 500k would represent the first year being sold out. Since they can't instantly ramp to full production, that leaves us with two options. Either the full-speed-ahead production at Fremont will be considerably larger than 500k/yr, AND Tesla anticipates being able to ramp to that speed aggressively, OR the number of reservations that represents the first 12 months being sold out is less than 500k.
I've been saying since we knew the 373k number that the first year or more of production approximately was sold out. Furthermore, I believe that reveal part 2, and possibly to a lesser extent an AP2.0 or Tesla Glass release could change the number of reservations dramatically. Never mind what will happen when the first deliveries start happening and people get a ride in their friend's Model 3. I believe that if you wait until you can actually see a Model 3 in a customer's driveway to place your order, you won't see your car until at least late 2019, and possibly into 2020.
For every person who is willing to drop a grand 2 years out, sight unseen, I am confident that there are between 3 and 20 more who will be willing to buy the car when they can actually see one, and even more still when I can buy one and get it in my driveway in less than 2 months. I don't anticipate you will be able to do that until at least GF2 and more likely GF3 is online.