It looks like the Panamera is getting quite a few updates for the 2021 model year.
There are some cosmetic improvements, updates to the infotainment, etc. All good, but what everyone really cares about are the engines.
There are lots of changes. These are covered in Car and Driver, simplified here for your tl;dr pleasure.
Panamera (base): Dropping the 3.0T for a detuned version of the 2.9TT, making the same 330 horsepower.
Panamera 4 E-Hybrid: Same as before. Detuned 2.9TT with a hybrid drivetrain. May receive a bump in power from 462bhp.
Panamera 4S: Same 2.9TT, may see a slight increase in power.
Panamera 4S E-Hybrid: New submodel. 4S engine tune with a hybrid system. Makes 552 bhp, more than the current Turbo.
Panamera GTS: Same detuned 4.0T, with a 20bhp bump to 473.
Panamera Turbo: Dropped from the lineup. Basically it’s been replaced by the 4S E-Hybrid, and...
Panamera Turbo S: Upgraded 4.0T, no hybrid system. Makes 630bhp.
Panamera Turbo S E-Hybrid: Now makes a nice, round 700 bhp. Still the same drivetrain as before, so this doesn’t receive the upgraded 4.0T that the new Turbo S model is getting.
I don’t think you can go wrong with any submodel of this lineup...as long as it’s a Sport Turismo :-P