Interesting thread to see how everyone is thinking. I went P85 picked up just before the release of P85D
, decided to skip P85D for the "next upgrade" but saw all of the 90kwh battery degradation issues and decided to hold on a little longer. Car was in the shop waiting for part for 3 weeks in which I had a fairly new P85DL which was great! Finally upgraded to P100DL recently, I won't comment on the cost-to-value to upgrade because its going to be subjective.
However, I will say if you can upgrade its definitely a better car than all performance variants preceding it. The refinement of the car overall is very noticeable, and to me makes the +suspension a non-factor just based on how the car feels in the corners. Again subjective but having driven lots of them I can say its my favorite so if you have the means definitely upgrade! The only consideration in the interim would be free supercharging, if that matters to you. This was one of the reasons I got mine before it went away, a few P100D's should be coming off leases soon so keep an eye out as they will have free supercharging on them.
Be mindful that there is a strong rumor that the "new interior" coming 2019-2020 will bring about further unification with the Model 3, and have 1 screen for both the Model S and X. This was a rumor at the beginning of the year that kept popping up and then v9 further confirmed it. If you are ok with that then wait, if not keep an eye on that CPO market....I am not a fan which is why I got it while I could.