DigitalCameraWorld has interviewed Canon UK executive during the EOS-1D X Mark III development announcement. Canon executive confirmed that EOS R Pro or EOS RX is in the working, and also confirmed that it will have IBIS and dual card slots.
From DCW:
“There’s a high-end EOS R in consideration,” said Canon UK’s product intelligence consultant, David Parry. “So we are considering bringing a high end EOS R to the market.
“If we do, it will have dual card slots, it will be that sort of level, and under development is in-body image stabilization. So we are looking at this technology, it is in development with us.”