I'm not sure I totally I agree with this. While totally blacked-out is probably not going to come stock from a manufacturer, black (or at least dark) rims are definitely an option these days from a lot of manufacturers as they seem more and more popular. (Plus wheel are easy because they can put on at final delivery)
My 2006 BMW 3 series had black window trim. It wasn't an individual option though. BMW actually saved the bright window (and grill slats) for the higher spec'd versions. I liked the black better. The kindey opening of the grill and model decals were the only chrome.
The only substantial chrome on the 3 will be the windows (and the connecting bit on the mirrors) They could certainly have an option for this to be dark, (we've already seen it) I just don't think they will in order to keep configuration options to a minimum.