1. The RF 85mm f/1.8 could be launched for far closer to the EF 85mm f/1.8 and/or offer advantages from the improved communication abilities of the RF mount.
2. The switch to mirrorless would be drived, as I wrote, by lenses EF doesn't offer, such as the RF 15-35mm f/2.8L IS USM, RF 24-70mm f/2.8L IS USM, RF 28-70mm f/2L USM, etc. The "business model" I suggest is limited to cheap primes, *if* Canon can't make new cheap RF primes instead. Which is my whole point.
As for the EF to R adapter, its a cheap extension tube intended to help photographers switch from EF to RF. As example, I have four L zooms. I don't have the money to switch all of them at the same time. The adapter will allow to make this switch gradually.
The adapter certainly isn't an item Canon can make a profit on long term, as lots of companies can copy it quickly.
3. Which is relevant to the point at hand... how?