Here is more info about upcoming Canon EF 200-600mm f/4.5-5.6 IS USM lens. According to CR, this lens will be announced at CES 2018 or CP+ Show 2018.
Canon has already filed a patent for this lens. And the rumored price for this lens will be around $1,700.00. This lens will not be an L lens, no weather-sealing, but will have great optics and build quality.