The Sharks, Stormers, Lions and Bulls have replaced the Cheetahs and Southern Kings in an upgraded and expanded Pro14 renamed as the United Rugby Championship starting in September.
The plan announced on Tuesday is for the South African sides to be allowed to play for the European club title from 2022-23, subject to contract terms being finalized with European organisers.
They join Pro14 sides Cardiff, Ospreys, Scarlets and Dragons from Wales; Leinster, Munster, Ulster and Connacht from Ireland; Edinburgh and Glasgow of Scotland; and Bennetton and Zebre of Italy.