An obvious assumption was confirmed by Canon in a conversation with Digital Camera World: no new EF lenses will be developed for the time being. Instead, the focus is now fully on the RF mount for mirrorless full-frame cameras, which will be introduced in 2018 together with the EOS R and for which the portfolio is still more than incomplete. To date, Canon offers ten RF lenses, including only two fixed focal lengths (50mm, 85mm), one 35mm macro and seven zoom lenses.
The situation is completely different with the EF mount, where you can find the right glass for practically every application -- from Canon itself, or from third-party manufacturers, now that the mount has been used for over 30 years. By the way, it is still supported by Canon, and should there be a demand for a new EF lens on the market, Canon will of course build it. But until then all signs are now on RF.