In Sun and Moon there will be a new method of training called Hyper Training. This will allow you to change a pokemon's IVs with bottle caps (we fallout now) once they hit level 100.

This is some crazy good news since now pokemon who may have been somewhat useless due to their awful IVs will be viable. This also means pokemon you gain while traveling won't need to be just throw away pokemon when it comes to the meta game. I'm personally extremely excited about this!