Despite the unusual timing, the move isn't a complete surprise. Given the new S4's recent switch back to a V6 -- and possible future move to an I4 -- it's plain to see efficiency is becoming a priority at Audi, even when it comes to high-performance cars. Similarly, BMW is rumored to be considering an I6 for its next M3, and the M5's V10 will soon be discontinued in favor of a twin-turbo V8.
According to a report by German magazine Autobild, the RS6 and R8 will follow the M5's lead and switch to turbo V8s in the coming years. That likely means the R8 will continue to come in two variants, but rather than a V8 and V10, there will be two V8 options -- naturally-aspirated and turbocharged.
Of course, these changes are not right around the corner. In all likelihood, it will be several years before Audi says goodbye to V10 power. Whether this proves to be the death knell for large engines remains to be seen, but Mercedes plan to phase out V12s makes this seem even more likely.