When I worked at Performance Ford magazine a year or so ago I was able to have a good long chat with the some of the guys on the RS Division at Ford, including a very interesting guy in charge of chassis development. He told me that with how well they can get FWD Focus to handle power now there is no point in doing 4WD, and round a track a vast majority of drivers would not be able to tell the difference or go any faster.

Based on that I very much doubt Ford will ever do a 4WD RS again, but you never know!