I upgraded to a D from an early p85+. I did luck out and get delivery of Next Gen seats front and back. I sit in the front always --- usually in the drivers seat. I like the front seats enough that I would have paid the upgrade cost for just the front seats, I believe they are that big an improvement. It does leave a bad taste to get less for the same money, but Tesla does change pricing all the time, as long as they offer the option of the back Next Gen seats to everyone who ordered when they were available I don't see an issue. Unfortunately I know first hand how aggravating it is when Tesla removes a previously listed option without a change in price. With my first Tesla the Tech package when I ordered had fog lights which were deemed useless at the time and removed from the package without compensation. Even though I use fog lights less then once a year I was still annoyed, human nature, or at least my nature i guess.
My impressions of the Next Gen back seats:
1) The rear vision which was never great, is more restricted with the Next Gen seats then the old seats in my p85+ due to the higher headrests, but I can't comment on how they compare to the newer performance seats now being placed in cars. For me I always used the backup camera and side mirrors, I have two teenage sons and as they have grown the height of the old headrests was a concern from a safety standpoint. I am happy with the tradeoff given the camera, sensors, and hopefully future auto pilot features. In an ideal world there would be a cutout in the headrests or the middle headrest would be removable as I only have two kids, so the middle seat is usually empty, but overall I am happy with the trade off of headrest safety for visibility.
2) My kids like the comfort of the Next Gen seats better then the old performance seats. With the recent attention I also have spent a few minutes in the back seat which is more time then I spent in 20 months in my P85+, in this short test I like the seats as well. So in my family we all agree that we like the Next Gen seats better from a comfort standpoint.
3) We do fold down the seats frequently, but I must not be very observant. I sold my P85+ several weeks ago without having the cars side by side I probably would not have noticed the difference in the folded position, I think the Next Gen seats have a little more of a bump when folded, but to my eye and for our needs (skis, snowboards) there is no difference.
4) Future wear, I have to think that the bolsters will wear more then a flat seat. The car is probably driven 70% of the time with one or two people. The back seat is used occasionally and the middle seat even less frequently so this isn't a huge issue. Even if it the back middle seat had constant use the comfort, safety, and appearance I would still choose the rear Next Gen seats.
I really like the Next Gen seats both front and rear. I am definitely keeping mine. Are they perfect? No, but overall I am really happy. Will Tesla improve the seats? Almost definitely, this being Tesla they are always tweaking stuff and changing things on a weekly basis. When will they make the change? Everyone knows the answer to that --- Soon. Of course we all know how Tesla defines "soon". Is it worth delaying a purchase to wait for the new and improved new seats? Not for me, but everyone has different priorities, I think the only thing the could sway my opinion of the rear Next Gen seats would be if I was still dealing with baby seats. I remember how much of a pain those could be and if the bolsters made compatibility difficult then maybe I would opt for the performance rear seat.