I think Jamaica would be champions of rugby 7s if they are payed and are taught well. 7s suits fast runners like i.e Fiji, South Africa and Kenya and Jamaica have a lot of athletes whom are quick. Rules, skills, techniques and strategies arent hard to teach and learn. Its hard to stop one fast guy in 7s because the size of the field allows him space and if your marking the fast guy he just has to run around you and then hes gone, now imagine 7 very fast athletes who know how to run elusively (side step, swerve, fend, run good lines hard) it'll be a nightmare.
I wouldnt be surprised if teams like Kenya and Jamaica began to constantly make cup finals in the future.