I think maybe some of the confusion/assumptions may be because the article stating "multi-turbo" S55 sounds like it might be more similar to the N54 than the N55 because the latter has a single turbo twin scroll setup not multiple turbos like the N54.
Having said that, I can see it now.....
"We have seen what the 3(M3) was capable of....now....prepare yourself for the POWER of 4! The all-new 444hp BMW M4!"
If only it was a 4.0l turbo, the advertising possibilities of the FOUR!