[source: Autoblog, A8 photo: Audi AG] A 621-hp S8 E-Tron could follow Autobild reports that the next-generation Audi S8 will be introduced later this year, and we've pieced together intel from various reports for an idea of what we'll get. Autocar says the coming D5 sedan will get a 4.0-liter twin-turbo V8 sourced from the Porsche Panamera Turbo, ditching the 4.0-liter twin-turbo V8 that Audi developed with Bentley and put in the current D4 S8. According to the report, the V8 will make 535...