Nah, LFP batteries would make the Model S absurdly heavy. Like 5500+ pounds. It would make no sense, except for a lower priced, lower range model, but that in itself would be useless, as demand is still off the charts for the new S and X, and they are currently maxed out on production capacity.
The next major change for Model S is the 4680 high nickel cells, along with the structural pack. This will happen likely sometime around 2025. Following that, I expect an all new Model S/X (including exterior), as we approach 2030.
What do you think the production constraint is on the S, right now? Weird that they're having so many issues producing Model S but 4 years ago they used to produce twice as many.