Nothing surprising here. I have been reporting Canon and Nikon have been working on their own full frame mirrorless camera for over two years now. In a recent NHK interview, a Nikon executive has confirmed the company's intention to bring such a camera to market by the first quarter of 2019.
Canon is also expected to announce a high end full frame mirrorless camera around the same time frame. Nikon's new camera is expected to require an adapter in order to use their F mount lenses. That is not very desirable. Canon already has such an arrangement with their series of EOS-M mirrorless cameras.
I have discussed how Canon can make their new high end mirrorless camera an instant success upon announcement. We will have to see how they intend to proceed with this important project. Keep checking back for the latest information and development.