Agree with the above...
The past options of allowing owners to go with pre and post announcement is a logistical nightmare for a manufacturing company.
As tesla grow they will rely on the just in time system... This means they won't hold more than days or week of inventory at any given time.
Easiest way is to just give everyone all the upgrade who's car has not been manufactured and it would seems ideal it would be any car before announcement.
This is a just in time manufacturing and just in time delivery system... If the above isn't the case it simply implies tesla parts are stored at the manufacturer and some how they are able to manage all parts at equal number for the upgrade...
If you were management, why bother?
Yes, this. There's absolutely no way that they are going to make different cars simultaneously. If there is a refresh, it will be a flash cut. The interesting question then becomes when to do the cut-over--before you announce it? After you announce it? Simultaneous with the announcement?
Each possibility carries with it the risk of pissing off customers, so my guess is that the new cars are either already being built (meaning the cut-over has already happened, as potentially suggested by the pics at the top of the thread), or that it is going to happen at the same time as the announcement.
I just don't see why, if you were Tesla, you'd announce the cut-over and then spend any significant time building "rump" early 2016 cars. Those cars are going to be impossible to sell, and lots of people with pending orders are going to cancel and wait, which creates all sorts of logistical issues.
All of this goes to show why "traditional" carmakers have stuck with the model year concept. It's easy and predictable, both for the companies and their suppliers and for customers. The "continuous improvement" model is great, but inevitably it means that some people will take delivery of their shiny new car only to be surprised days or weeks later when it is suddenly obsolete.