There is only one guy who can beat Rafa on clay, and we all know it is Djokovic at the top of his game. There's no way we can say for certain that Djokovic will win Roland Garros this year, as Rafa still rules over the French Open, but the advantage Rafa has over Djokovic has reduced every year since 2011.
As a Rafa fan the most worrying thing about the match yesterday was how easily Djokovic neutralised Rafa from the back of the court, and how timidly Rafa played him throughout. The dynamic is different on clay since Rafa has more time to run around his backhand, but that tendency was severely exposed by Djokovic's incredibly precise backhand throughout the entirety of the match. No matter how strong Rafa is on clay, winning Miami so easily will give Djokovic massive confidence going into the clay court season and I can imagine that he will win another final over Rafa yet in a clay Masters event.