There are only a few things known about the upcoming Tesla Model S and Model X Plaid variant. We know that the vehicles will be frighteningly quick on the track based on tests from the Nurburgring, and we also know that the cars will have a tri-motor configuration like the next-gen Roadster. Elon Musk has also mentioned that the Plaid S will feature a seven-seat option.

Yet apart from these, specific details about the Plaid Model S and Model X remain unknown. Fortunately, the Tesla community's resident hacker, @greentheonly, has discovered a number of references pointing to new hardware that is coming for the Model S and Model X. Considering that the Plaid S is poised to be released later this year, some of this new hardware may very well be equipped on the upcoming vehicle.

New hardware incoming.
Integrated inductive phone charger (Qi) for S/X cars.
Two new S/X battery types in several configs (not yet sure of the capacity - TBD)
new lumbar (so new seats?)
New charge port type.
New suspension version.
I would speculate all these are imminent 1/

— green (@greentheonly) January 25, 2020

According to @greentheonly's research, the Model S and Model X will be equipped with an integrated inductive Q1 phone charger, making it easier for drivers to charge their phones while in their vehicles. A new charge port type, new suspension, and potentially, new seats, were also mentioned. Yet, perhaps the most notable of the Tesla hacker's recent leaks involve two new Model S and Model X battery types in several configurations.

Arguably the most significant leak part of @greentheonly's leak involves the new batteries for the Plaid Model S and Model X. The vehicles' performance on the track has suggested that the flagship sedan and SUV will be equipped with batteries that are superior to the current Raven S and X's 18650 cells. The new leaks only hint at new batteries, of course, so it remains to be seen if the Plaid Model S and X will feature dry electrode tech from Maxwell, or perhaps the company's 2170 cells used in the Model 3 Performance, which are track-worthy.

The Model S and Model X have largely taken a step away from the limelight as Tesla focused its resources on the Model 3, and in extension, the Model Y. Yet, the S and X remain as Tesla's flagship vehicles. It is then quite encouraging to see that Tesla is indeed looking to roll out massive improvements to the Model S and X soon, and on the hardware front too. This would likely result in more interest and sales for the vehicles, as they would have specs that far exceed that of the more affordable Model 3 and Model Y.