At the end of the day, there remain values for redemption, but dynamic pricing changes which fares are good value.

I suspect that dirt-cheap redemptions in long-haul premium cabins will become increasingly scarce, if not disappear completely. The prior pricing was way too low relative to the cash price. Part of this was due to a glut of premium cabin seats on some airlines - I'm thinking of the KE A380 J cabin or the old LH redemption class, I mean F. Even the US airlines were guilty of this and I think UA still is. As airlines rationalize capacity overall, and reduce premium seat counts in markets that don't support it, it will reduce the opportunities for low-cost J redemptions.

That being said, I think there remains some value as airlines adopt dynamic pricing. A lot of short-haul flights can deliver good value, particularly on business routes on off days. Even without dynamic pricing, we saw this with BA a while ago as they adjusted reward pricing to distance-based pricing and better aligned premium cabin reward pricing with cash price differentials.