There will not be a Zen3+ on the desktop. The two V-Cache-Chips in 1HY22 will be based on regular Zen3.
As known so far, AMD has canceled Zen3+ on the desktop. Rembrand will use Zen3+ for the APUs in 2022.
And for the rest, its all speculation and workload-specific. The top ALD CPU may still beat the 12-Core-V-Cache-Zen and the rest simply depends on the price (the same principles, which allowd AMD to survive in the last decade ;-)).
Zen4 again is a different story, because it has to compete with Raptor Lake and here again it remains to be seen what is relevant at the end for common workloads. Fans often tend to ignore that for consumers/gamers AMD has only managed to get "the performance crown" with Zen3, which is only a few month ago. Up to Zen2 Intel had no problem, even with their older Skylake-based architecture in 14nm, to compete against AMD and that is most likely the point at which fans eagerly throw the unbeatable 16-core-Ryzen on the table, but its relevance is small for the majority of the consumer market.
Just wait an see. We now have e healthy competition, Intel should be in the final steps of solving its manufacturing problem and we can expect even more powerful CPUs in the near future ... albeit this may not be of big importance for the over all market. ;-)
"The best scenario would be AMD and Intel both trading places in lead, alternatively."
The best for whom? For consumers, for AMD, for you? Who decides what is best? And why should the firm with the more limited resources take over? Such whishes make no sense.
And you seem to forget: The more AMD manages to establish itself, the more expensive their products will get. The only reason why e.g. Ryzen's have been "so cheap" in the past ist due to competion and gaining market share (as the underdog) and not because AMD is soo nice and friendly to its customers, almost altruistic. ;-) AMD wants exactly the same as Intel or Nvidia, there's no difference regarding to this point ... ok, to be exact, the difference is in the head of some customers, but this is more of a psychological topic and has almost nothing to do with technical details or market mechanics.