Tesla’s new Li-Ion battery will probably fit older S & X.
You don’t have to wait. Ohmmu has been selling Li-Ion batteries for S & X, also 3 & Y for years. They have a strong reputation. One stumble when the Model 3 battery internal control system didn’t work well after a Tesla update. They did free battery swap for affected customers.
We got a 12 Volt battery warning message on our 2017 S 100D last Fall. Ordered the battery and installed it in relatively short order.