User blog comment:Smasher51/Leaked Fotage and Screenshots for Roy (Fire Emblem) and Ryu (Street Fighter)/@comment-24128208-20150613200822

Maybe Ryu would be an easy character to make in Smash since he comes from a fighting game. Also, Roy would be an easy character to make too because he is a clone and he was a character in Melee.

Another reason could be the new Street Fighter but it's not on a Nintendo console. I'm not too sure about Ryu's reasons in Smash.