According to Car and Driver the all-new S4 could benefit from "twin-charging" with the possible inclusion of a turbo in addition to the supercharger. It is expected that Audi will unveil the S4 at the Los Angeles Motor Show in November.
The S4 is also tipped to get a Magna-sourced "sport differential" like the ZF unit featured in the BMW X6.
All of these new attributes will enable the S4 to rival the BMW 335i, while the RS4 takes on the M3.
Power will likely remain similar to the outgoing S4's 253kW but its weight will be slightly reduced. The purpose in switching to forced induction would be to improve fuel economy while returning comparable performance.
Car and Driver reports that the S4 is also expected to be developed outside Quattro GmbH, while the RS4 would be created by the Audi performance division.