Originally Posted by EniLab

Turbo engines are here to replace large displacement engines. E.g. 3.0L I6 turbo instead of 3.5L I6 NA. Or 4.0L V8 turbo instead of 5.0L V8 NA. Etc.

We will see two engines of a same displacement: one NA and one turbo. This is the strategy.

E.g. 1.6 + 1.6 turbo instead of 1.8 NA, 2.0 +2.0 turbo instead of 2.5 NA, 3.0 + 3.0 turbo instead of 3.5L NA, 4.0 + 4.0L turbo instead of 5.0L NA, 6.0 + 6.0 turbo instead of ??? NA , etc.

That X5 will get V8 turbo in "S" model is just a coincidence.
Eg. the new V8 turbo will be featured in "non-S" models of e.g. new 6er, 7er, 5er, V5, X6.