I see what you are saying, but you are not taking architectural improvements into account. Look at the difference from Maxwell to Kepler, both 28nm as I recall?
My guess is it will come out 2020, don’t care what JHH says, he said something like that about 4-5 months before Turing came out also. I expect the 3080 will easily beat 2080Ti performance and trounce the RT performance.
Well personally I think the "much cheaper" aspect is extremely unlikely to happen. AMD don't want to be much cheaper these days.AMD will have videocards that are faster, much cheaper and drawing less power than RTX 2080 Ti in 2020.
Second they have just about matched nV's performance and power usage with a significant node advantage. When nVidia reduce that advantage suddenly AMD are going to pull away out of sight? Again, that doesn't match with reality.