I think that from September 30th to October 30th Suicune is going to be in the Americas, while Raikou moves to Europe and Africa. Then Entei moves to Asia and Oceania. It would benefit some Pokemon Go players, but not all of them. Raikou would be super effective against Suicune if it goes to the Americas. Suicune would be super against Entei. Entei would not have any additional effect on Raikou though.