It would be helpful and encouraging if Canon produced a timeframe and list of lenses that they plan to release in the next 2-3 years, but plans often change, due to development issues, supply chain issues and various other factors, so I don't think we're likely to see this happen.
I agree completely that there needs eventually to be a middle-tier of high quality Canon glass, with modest maximum apertures, high build quality and sensible pricing. At the moment we have two extremes - expensive L exotica, or "affordable" lenses such as 16mm F2.8, 600mm F11 etc. But Canon is prioritising the lenses that it believes will sell in the largest numbers and bring in the highest profits. I think eventually the middle ground will be filled, but it isn't going to happen for at least another couple of years, as they haven't yet filled out the L range or the budget range.
Overall, Nikon glass is at least as good as Canon glass, and in some cases better. I can't see Canon or Nikon allowing the other to use their protocols.
Same for Olympus - their Zuiko lenses are incredibly sharp, extremely well built, very light, compact and sensibly priced, so why would an OM user want to slap Canon glass on?