RDNA 4 is rather an improvement on RDNA 3
The new generation of AMD video cards will remain without flagship adapters. It is not yet known what AMD has decided on this matter with the generation that will appear after the coming one, but it is reported that the RDNA 5 architecture, which will be at the core, is completely new.
RDNA 4 has completely new ray tracing units, which should make Radeon RX 8000 video cards more competitive in this regard against GeForce cards than the current and previous generations of AMD adapters. But in other respects, RDNA 4 will be more likely to work on the errors that RDNA 3 had.
But RDNA 5 as a whole will be a completely new architecture, which could allow AMD to make a significant leap in performance and energy efficiency. It is likely that AMD decided to abandon the top RDNA 4 GPUs, among other things, in order to free up more energy and concentrate more on RDNA 5.
Also, insider wjm47196, who was previously the first to talk about the updated Radeon RX 6000 models and some GeForce RTX 30 cards, explained why the Radeon RX 7000 turned out to be quite controversial. According to him, the bottom line is that the final characteristics of the RDNA 3 architecture, implemented in silicon, were not as good as on paper. The cards turned out to be less energy efficient, which is why, among other things, AMD had to halve the amount of Infinity Cache memory compared to originally planned.