really funny how some folks misread the current situation.
Canon has moved to mirrorfree cameras. Transition will happen fast. There will be no more new EF-S lenses because they have already been fully supplanted by EF-M lineup. There will be no more new EF lenses, but at best a few minor iterations of existing ones to make them fit for use on mirrorfree EOS R line. Typically long teles that don't profit much from shorter FFD mount.
All the attention has shifted to building a compelling RF lens lineup. Canon has no choice, they want to be #1 not only in mirrorfree APS-C, but also for FF. they need to keep ahead of Nikon and catch-up/pass Sony.
Also: long "L" tele lenses are an extreme minority program, despite all the birders in this forum. 99% of Canon customers do not own one and never will. there is no need to design an entire new camera/ lens ecosystem just to please 1% of potential customers. it would make very little sense business-wise. for every 1DX II + 600/4 customer there are literally thousabd others who would like ro get a supercompact, 999 USD "entry level" EOS R model along with some decent, compact and well affordable RF f/4.0 zooms in the most frequently used focal length range. RF 16-35/4, 24-85/4, 50-150/4 zooms would all be selling very well.
For the "big lens, big hands,, big wallets" niche I expect Canon to bring a mirrorfree "1DX III equivalent" EOS R "pro" camera - at the latest in early 2020 ahead of Tokyo Olympics. It will be large-bodied, cost close to 10k (25% more than 1DX II, simply because it is new and hype) and be the perfect camera to attach massive white L 10k+ telelenses. Big chunky body and grip, big battery, maximum performance, EF glass usable via little adapter.
so, where's the problem?