Its my opinion that, you wont see anything "special" at all for SR owners as that car is (was) a compliance car for tesla. Meaning, I doubt you will see any push to lower upgrade costs, or anything else for that specific model.
Again, no one has a crystal ball, so no one knows, but its my opinion that if tesla was ever going to consider lowering that upgrade price, they would have done it already when they made the price of the SR+ less than the cost of an SR+ the upgrade. They didnt change that, at least not now, and I dont see them changing it going forward.
That car is as much an "orphan" car as the MR (Mid Range) model, imo. On the Mid range, though, it has everything that the LR ones have except the range itself (premium interior, etc). Both orphan cars, both likely to see little support other than repairs, in my opinion.
In your specific case (the car says its a sr+ but thats not what you have), its entirely likely that if you did that, tesla would "catch the error" on title transfer and downgrade the car to an SR "properly", then some person would be on these (and other boards) complaining about how tesla "screwed" them, etc.