Nvidia has quietly did this on a few previous series where they change out the GPU without changing a card name. At most is you'll see a minor change on product SKU. The devil is in the details, so it pays to research specific cards for specs.
People also need to make up their minds about the story of GPU supply. Either the retail prices dropped so much for 3000-series vs 2000-series because of good yields out of Samsung, or the yields are so bad they're hedging their bets with TSMC. It can't be both.
My thoughts on AMD. My guess is they could of paper launched already and it would of turned out like Nvidia did this launch, so they're sitting on it till they can do it right. The best lessons are learned by watching someone else screw up epicly and knowing enough to avoid that same fate.