AutoCar is one of the worst information sources.
3-door Fiesta in the US? Not a chance. The car needs to be recertified at a very large cost, plus changes to the NA assembly line.
AWD? Not likely. Cost and weight prohibative.
Significant price and performance overlap with the Focus ST. It doesn't fit a well positioned product in the portfolio.
No evidence of a Fiesta RS mule has ever been spotted. Mules show up about 1-2 years prior to release, unless the case of the Ford GT in which no mules were made in advance. Fiesta ST mules started showing up in 2011, Focus RS mules in early 2014. Fiesta chassis redesign due in a few years, so the Fiesta RS lifespan would be limited to a year. This has happened in the past, but it is unlikely you could build a buisness case to support all the development for a product with a year of sales.
My contacts have said for years that it would be either a Focus RS or Fiesta RS, but highly unlikely there would be both. The nod always going to the Focus RS with larger platform and higher price point.
I am putting up the BS flag until test mules or a reliable source can be found.