Canon Rumors is reporting that distributors have received some early information about Sigma’s plans for RF mount lenses for the Canon EOS R system. Beyond that, there isn’t really any more information, except that CR expects there might be an announcement ahead of CP+ in February. They don’t name their source, but they have ranked it as “CR2”, which sits somewhere around the “Ok, you have my attention, but let’s see how it pans out” level.
But it makes sense for Sigma to be pursuing the RF mount. It’s become quite popular, especially in Japan, where both Canon and Sigma are based and it’s also the mount that’s coming on the RED Komodo cinema camera.