I think that leaker is full of crap. AMD may well fix bugs but RDNA4 is much more than that and will be highly competitive in the mid-tier market with 7900XT+ raster and much improved RTing over RDNA3.
AMD is expected to release new RDNA 4 GPUs sometime later this year. Based on the Navi 48 and Navi 44 chips, RDNA 4 reportedly won't have any high-end offerings as the company is focusing primarily on RDNA 5. A new rumor posted on Chiphell claims that the RDNA 5 is similar to the Zen series in its design ambition.