We have the EF-S and EF-M lineups for comparison. While there were some 'high end' lenses in those lineups, they were few and far between. The EF-S 17-55 was launched early in Canon's APS-C lens history, and never updated nor moved over the the M line. The EF-S 10-22 that was pretty close to constant aperture (f/3.5-4.5) was updated with the slower and lower build quality EF-S 10-18. With EF-M, there were no constant aperture zooms. There were two fast primes (22/2 and 32/1.4), both of which are very nice lenses. But for zoom lenses, mirrorless opened up the possibility of slower than f/5.6 at the long end...and Canon took that bull by the horns with EF-M and RF-S.
On the body side, the 7-series has the longest update cycle of any Canon ILC series. Many people here clamored for a 7DIII, Canon never delivered one. Together with the limited efforts on 'better' APS-C lenses, it suggests Canon has no real appetite to serve the high-end APS-C market.
Given that history, I do expect we'll see an RF-S prime or two, but probably no constant aperture zooms.