Here's an article that has, I think, a better take on all this. I think New York Magazine allows a few views without pay? (I'm a subscriber.)
Banks Don’t Like Paying You So Many Credit Card Rewards — But They Will
https://nym.ag/2TpCWvi
The gist of it is that rewards will continue, although perhaps with less generosity (they've already had to pull back on things like unlimited PP guests for Sapphire Reserve). Merchants are really the ones paying for our rewards, through transaction fees. Lots of stuff I didn't know: for instance, Signature Visa cards charge merchants a higher transaction fee than regular Visa, but Visa Corp. requires merchants to accept all or nothing. There's currently a lawsuit by merchants trying to allow them to defeat these requirements and allow them to choose exactly which cards they accept. The big credit card vendors (including Amex) are actually getting together to discuss how to deal with the rewards situation (sounds like that should be a huge anti-trust violation, but I'm not a lawyer). Amazon may be on the verge of switching to a one-brand-only policy like Costco, in order to control transaction fee expenses (OK by me, since I'm buying Amazon gift cards at the grocery story anyway).
The sky is not falling, but the landscape is ever changing.