Speculation is flying fast and furious, but I think Tesla is just opening free supercharging for life back up to all S and Xs and that will be a benefit of the high end car for the foreseeable future. This will include CPOs, owners of any S or X who upgrade to another S or X, and pretty much any other owner of an S or X with a clear title.
This will not cover people with salvage title S or X and it won't cover Model 3s or other mass market cars Tesla makes. This does make a clear benefit to shell out the extra money for the higher end car and helps to distinguish the S from the 3 more clearly. People who can afford the more expensive car and plan to do a lot of supercharging, it may make sense to shell out the extra and get the higher priced car. For those who are not going to be road tripping much, or have more limited budgets can settle for the less expensive, mass market car.
Tesla probably caved in and gave up on the paid supercharging for the newer S and X because they were seeing a clear decline in sales after free supercharging ended and the cost to them of providing it is less than the sales drop. Opening free supercharging back up is a cost to them, but most people don't use much more than the 400 KWh allowance a year anyway. So far in a year I've taken one road trip to California, and used superchargers three times on day trips. I did use 560 KWh on my California trip, but about 80 KWh of that was AC charging (at home and a destination charger at a hotel). If there were more convenient destination chargers I would have used those and used supercharging even less.
So I have gone over by about 100-150 KWh in the last year (between the trip and the day trips), but the last time I used a supercharger was in October. At the rates Tesla was going to charge, I would have been out $12-$18. Even if Tesla is just breaking even, they are only losing around $20 a year over what they would have given me for free if I was on the paid supercharging.
They looked at lost sales and lost good will and probably figured for most of the fleet they were looking at around $50 a year in supercharging. A few heavy users are costing them several hundred a year if not over $1000, but for a couple of those heavy users like Bjorn, they are getting a massive ton of publicity from his videos. So instead of shelling out lots of money on TV ads, Tesla is giving away long distance travel and letting people brag to their friends about it.