I am one of the few that chose After December 1. In fact I would have been tempted to choose 2016 if that was an option.
There are many people here who are lot more informed than me. So I might very well be wrong. But FWIW here is my reasoning:
Looks like Tesla planned to release the car without 2nd row seat folding. But after seeing the reaction, they ought to fix this before release. I really see no way that signature folks get their cars without folding seats.
It's a HUGE issue for multiple reasons:
1) Elon promised that he will never ship a non-compelling car/product (this was when 40kWh was getting deprecated).
2) Elon promised that production car will always be better than demo cars. He mentioned this multiple times actually. In interviews/CCs and on twitter.
3) Many (uninformed) people will feel that it's a bait-and-switch to suddenly realize that the seats don't fold. What if people notice this well after taking delivery and are shocked? In this litigious society, opportunistic lawyers will certainly see blood in the water. Class-action lawsuits anyone? Sure Tesla can pre-empt this by "clearly" communicating this up-front before or during taking delivery. But clear communication seems to be the last thing Tesla is good at.
4) If many months later they fix this to boost demand, how will many signature holders feel with the wrong seats? They are promised, they are not given, then everybody else after them is given the right seats. This will not be right at so many levels.
In a nut shell, I fully expect them to fix the seats before the true launch (founders series doesn't count).
So now we are talking about back to the drawing board and re-designing the seats. Design, implement, test, productionise, and maybe multiple iterations of that actually. This will take several months.
For reference, Tesla took 6-months to launch the Titanium underbody from the first f!re incident, which should have promoted them to start exploring a solution. It's a seemingly simpler issue.
Put this all together, we have an early 2016 launch.
On a separate note, I am also very suspicious of all these cgi screenshots in the design studio. Why not real pictures? They didn't want a single photographer to be able to see the car? Ok, even if that's the case, nobody in-the-inside is capable of taking a decent picture? really?
Think about this, how much harder is generating a fake cgi picture, with a bike and everything, than a simple click on a camera? The only thing I can think of is that the car is not ready.