Apologies if I offend sensibilities with the heavy-handed nature of this response, or if it seems a bit extreme, but there are some considerations in answering this question that I have not seen mentioned here that to me are quite important:
I think that those that say these jump seats are unimportant are not thinking in visionary terms, particularly when they make comments like "just wait for the Model X." Sorry to say it, but that is Detroit thinking IMHO.
Detroit fails in many cases because it gets into a paradigm for a given vehicle class and then cannot think outside the box. Hummers were the ultimate example of this, and a good chunk of America was along for the ride, suffocating mother nature in the name of bored trophy wives' mall parking bling. About the only legitimate purchasers of that car were the military and backcountry tour operators with very few exceptions. Otherwise they were pretty much pure vanity as there were many other options for interior space and off road capability if you just needed a car to get the kids up to a ski slope or something.
Elon has come along and been an outside the box thinker from the start. He is redefining what a sedan is / can be.
In the past, if you wanted to seat 7 for your kids' soccer carpool, then you had either an SUV or a minivan to choose from. Neither are very green. In dys of old you could buy a station wagon and throw kids in the back if you were not child safety conscious, or throw them in the back of a pickup truck. Outside Native American reservations though these solutions are generally frowned upon these days in the interests of our children, for good reason (on the res there are other considerations but they are beyond the scope of this discussion and way off topic). If you see a few kids from highway accidents that were not properly restrained, then this is very quickly apparent. So in the name of safety and practicality we were sold the notions that SUVs and minivans were our only modern options.
If you wanted an electric car, you needed to sacrifice the # of passengers and performance compared to other standard sedans, let alone a sports sedan.
But now with the Model S, we have a combination of a sports Sedan, a minivan, and a green EV with performance and utility that is astonishing... all because Tesla dares to think outside the box and not be beholden to oil merchants like Detroit is, or to thinking that definitions of a given vehicle class are rigid. To suggest that one should wait for the SUV to have a 3rd row is thinking like typical auto manufacturers.
I already have a minivan because I am at that soccer carpool stage of life. If I could have bought an electric one with a reasonable range I would have. This car is replacing an SUV for me. The jump seats are a deal breaker. And whether your family needs them or not, they are very important to the success of this car and in being a catalyst for outside the box solutions in the auto industry instead of the same old crap that has had us locked into earth-killing, troop-endangering ICE vehicles all this time.
So, while I am clearly showing my political leanings, I think that it is possible to have our cake and eat it too... quite in defiance of the mantras originating from the motor city all this time. Tesla is proving that. And I think anyone can agree that if we don't wreck the economy to do it, then passing on a breathable atmosphere with a pleasant climate is an important thing to do for our great great grandchildren, and putting people in danger or leaving one's country politically beholden to another that is less scrupulous simply because they have something you need are all things that should be considered in the car design and purchase equation. And a few of us might even think that trading some of the economy for these things is sometimes reasonable, but again that would be way off topic and far too political.
In any case, these jump seats are important in ways far beyond whether any one of our families need more than 5 seats. Hell, most of Utah could switch off of SUVs and minivans with this car, and they have plenty of sun for solar panels so they could do it without any need for oil if they so desired.
This is certainly not the first car to use jump seats. Volvo, Land Rover, and others have done it in the past. But the combination of all these attributes is something you won't find in a Panamera, a Sienna, an M5, or a Leaf. And you certainly won't find this all blended in something coming out of Detroit any time soon. Tesla is setting a new paradigm here and one in which the jump seats play a fairly big role. They set our to prove that an electric car can be the best car in the world. The right car for everyone. I think they are on the cusp of succeeding, which although strangely missed by a certain ex presidential candidate has been well recognized by others with expertise in this area, such as Motor Trend, Automobile Magazine, Yahoo, etc... as well as those who have already taken delivery--even without having the jump seats yet.
So to summarize, the jump seats are quite important IMHO.
Having said that, I think that the chances of them not ever becoming part of the car are next to nil. Elon is a bit stubborn when it comes to innovations. So glad that he is.
Just my 2 cents.
Cheers
