Kirby Battle Royale is already out in every region, but Nintendo decided to hold a poll on the next copy ability, to be added in a future update. Yo-Yo and Suplex lost out to Sleep! This follows the win of the Mirror copy ability, added in as post-launch content.
Lest you think that the Sleep ability is a useless little thing — a joke character if you will — take a look at the video below. Kirby sports pillow attacks, life regain through napping, bubble powers, and the ability to put people to sleep. He seems viable in every situation with group crowd control and the power to heal in 1v1s.
Nintendo of America [Twitter]