I seriously doubt the veracity of some of this. What will be common with the n55, the block alone or a bored out version of the block with larger displacement?? Probably almost all internals would be different. It is terrible marketing and the car has a much poorer chance of success if it is called an revamped n55 or if that is actually what it is. There is simply no way they will lightly tweak the n55 change the boost and call it a day. As stated earlier the n55 share a ton with the n54 and that engine is too old to be reusing that much of it.
That being said the poster about 3 engines for the entire line up is correct. Well maybe the number is not 3 exactly but this is BMWs plan - massive reuse of common components for many more models. This is their road to much more profits. Pure and simple.
Now at the same time I fully accept the veracity of the rumors that the car will have a relatively low CF content. I've been strongly promoting that argument here in this thread