This story originally came from a relatively obscure German blog and then went all over the place. It's not certain if it will be available yet here at the moment, and the official Daimler media website says nothing about it for the E63 as of today.
I'm partial to NA motors and glad that the M156 will still be in the C Class, and the M159 (based in the M156) will still be in the SLS.
This M157 5.5TT is not an AMG designed motor and is based instead on the new M278 used in the rest of the Mercedes fleet. We all know this is primarily all about costs and CAFE regulations, and getting power with okay mpg and out of a smaller package. Plus there will be DFI, stop/go, and no gas guzzler tax. So it also becomes a better sales and profit issue, too.