In reaction to a writer's suggestion that he take a guest referee spot for the upcoming match between Matt Riddle and Seth Rollins, Ken Shamrock voiced his support for the concept, as you can see in the tweet below. The live event is scheduled for October 8 in Philadelphia, PA. According to Shamrock, he "Couldn't agree more!" to the idea that he take part as the ref for Riddle and Rollins. Shamrock's last appearance with WWE took place in 1999, but he stayed active for a time with UFC and NWA after leaving the promotion.
https://twitter.com/ShamrockKen/status/1572061953429999619?s=20&t=FzZX_HX87ULOAaCTmpS7vw