As Tesla faces more competition for long range EVs, the major factors will be features, range, performance and cost.
One problem Tesla currently has is differentiating 3/Y from S/X - since the 3 (and future Y) have almost the same feature set as the S/X, but at a much lower cost, with some loss in interior/cargo capacity.
In the near term, we're likely going to see V3 supercharging, which probably needs the newer 2170 battery pack designs. Phasing out the S/X 75 battery packs is likely the first step towards introducing new battery packs for S/X - which will bring S/X to the same level of battery capabilities as 3/Y (right now S/X is using the older technology).
2170 packs are smaller and cheaper per KWh, so that opens the door to lowering the price of S/X 100 vehicles (or increasing profit margin) and possibly introducing a slightly higher capacity S/X battery pack (which would add something to S/X that won't be available in the lower priced 3/Y).
When the new 2170 packs are introduced for S/X, wouldn't be surprised to see the price of the 100 models drop and a larger pack (120?) added at the same price as the 100 models today. This is what Tesla did before when they introduced the 90 and 100 packs.
And they need to do this before they deploy V3 superchargers, or risk leaving out their higher end S/X models from the faster charging. [Of course, current S/X owners may not get the full benefits of V3 supercharging, while all Model 3's may already have the hardware to support faster supercharging).
Also wouldn't be surprised to see Tesla add a few new features to S/X, to further differentiate from 3/Y - so that stepping up to S/X from 3/Y would add range, performance, and features - in exchange for the higher cost.
Though with Tesla's focus on expanding their product family - Model Y, semi, pickup and Roadster 2.0, still seems likely they'll hold off on any major changes to S/X for now, and wait until they are closer to having FSD working before they do a major interior redesign.