One of Jalopnik's readers snagged a photo of a BMW 5-Series with a 555i badge all over it, parked somewhere in Long Beach, California. We have heard rumors in the past of a BMW 555i based on the existing E60 platform that will sport a Twin-Turbo V8 engine. The same engine is used in the BMW X6 xDrive50i, so the possibility of having the same engine in the 555i was quite high.
I personally highly doubt that BMW will invest any more time, energy and money in the testing of this engine on the existing E60 series. The next generation 5 Series is just around the corner, so within a year, we might actually see the Twin-Turbo V8 400 horsepower engine but on the new F10 platform.
Pretty cool badge though and I'm sure it draws some attention, especially at BMW meets :)