To unlock the "40"kWh pack to 60 plus Supercharging seems to be about the same as just upgrading to a 90kWh battery, now. Those unicorns running around are looking better and better as a used car, now That's a 125% increase in battery capacity! Double the car for a fraction of the price! EDIT with title change: Yes, Tesla did allow an owner to upgrade his S60 to a P85 in the past. However, they want you to upgrade the whole car, now. The trade-in value for a 60 (or "40") is too low to make any sense. Factor in the requirements of Supercharging and you really might as well just switch cars. That being said, for existing owners with 85 or 90kWh batteries, it will make sense when 100+ comes out. Swapping from 85-90 doesn't make a ton of sense, but it is possible. Additionally, the upgrade from an existing P85D to P85DL includes new fuses, contactors, and labor to handle the new 1500A level.