There will be a tremendous performance hit for AMD users.
Then I will get an Nvidia card. The hardware exists to serve my gaming needs, not games to suit my hardware needs. Sell one, buy another.
I do this, if I do this, (have I ever done this...hmmm, I don't think I've needed to, yet. Oh, wait..yes, but I gave the other card to my brother in law), only when a major game comes out and only if it looks like a severe loss or graphic problem is an issue.
I doubt the AMD hit, if any, will be worse than 10% or so, since CDPR will have an interest in you having a smooth, fun, gameplay experience. Will you get as high as some other card by some other company? I have no idea. Will it play smoothly is a more pertinent question and, frankly, if you are pushing your card limits, no it probably won't. No matter the card you run.