There'd be zero surprise from me if AMD just doesn't release a Threadripper 5000. They don't need to because Intel has nothing in the HEDT space, and I don't really see many Threadripper 3000 users crying out for more performance like their kit is deficient in some way. With substrate shortages as horrendous as they are, it makes more sense for AMD to direct their limited capacity to markets that "need" Zen 3: the EPYC steamroller must continue, the desktop domination must continue and efforts in the laptop space must be bolstered. HEDT is a niche that's already in the bag, there's nothing to gain in the short term by taking resources from elsewhere.
That being said, it's looking like Zen 4 has been pushed back in the face of Intel offering nothing of substance for a while, giving AMD room to experiment with a few things, the cache-stacked chiplets being a prime example. To that end, maybe AMD are waiting for the 3D chiplets to mature and use those in Threadripper, holding off long enough to see what the Sapphire Rapids HEDT products offer. Certainly any gains Golden Cove will bring in its Alder Lake guise will be countered purely with the 3D stack Zen 3 enhancement, likely the same thing will apply to Threadripper.