The bigger you go, the lower the payoff for additional die size and shaders because clocks tend to suffer. This may be less apparent on 7nm and depends on architecture as well, but still, it won't ever be the reverse of that, at least - even on Pascal and Turing you do see the midrange SKUs clock somewhat higher than the top-end.
But as
@efikkan points out, TDP budget is going to be a problem once again. 7nm doesn't change that all that much, and if you remove the node and just look at architecture AMD still has work to do. Perf/watt is still a thing and again, we're only even comparing this all to OLD Nvidia stuff - while Navi 20 is yet to release. Timing. Time to market. Relevance. Did you seriously think Nvidia is just now taking a look at what to do with 7nm? I surely hope not... If you were, be ready for another Kepler refresh >>> Maxwell curb stomp because that is very likely the jump we will see there.
The reason people with a 300-400 card budget are looking up at the halo cards is because that will indicate how worthwhile that 300-400 dollar purchase really is. After all, if performance just about flatlines after, say, a 2060, why would you spend 700-800 on the 2080? At the same time, today's 700-800 card is tomorrow's 300-400 card (simply put).
Progress in the high end matters, it is essential to keep the market moving forward. What we are seeing since Turing is
not that and the result is price ánd performance stagnation. Since Navi will be too late to even matter in that sense, even Navi 20 catching up to 2080ti is unlikely to make a difference, unless, again, AMD is willing to play the value game they really could play with these GPUs due to their size.