The platform in question is know as CD6 and, as the article states, will underpin the recently shown Lincoln Aviator (the concept is a stunner) and the '20 Explorer. As soon as it was rumoured both these were going RWD (with AWD optional) it was pretty obvious Mustang would utilise this architecture.
Personally, I think this is where the scaremongering of "S650 is dead" came from last year. For all we know, they may well still call it S650, but utilising this new architecture means the Mustang's launch was put back a year from '21MY to the now expected '22MY.