1. AVX512 is extremely niche, and will remain that way for a long time.
2. Golden Cove is a long way out for servers. We're talking Granite Rapids, which is late 2022 earliest (as it's 7nm). For desktop and mobile, it's relatively soon, but for servers? Yeah, 3 years of remaining on top is almost guaranteed. Sapphire Rapids is
almost confirmed to be Willow Cove.
Well, this is about as close to a confirmation as one can get bar actual word from Intel.
3. See above, plus, what makes you think AMD doesn't have 3D stacking coming relatively soon-ish, or that Intel will be utilising Foveros at all in the near future on the server platform.
Granted, it's a TSMC tech that AMD may or may not use, the option is still there for AMD to utilise it. Whether they will or they won't is yet to be seen.