In my opinion, the fact that the Modern cards get a 50% nerf on their PP is a strong indicator that the plan was always to eliminate that nerf when they rotated out of Modern. Otherwise, the new Modern sets would have always been at 1 and the previous sets would have had bigger multipliers (Chaos=2xPP, Untamed=4xPP, etc). I was always under the impression that this would be the case.

If the team has been building and doing all of their calculations with this as their baseline, I don't think it would be a good idea to change the original plan.

As others have stated, if each new set continues to have discounted PP, then the future value of owning those cards after they leave Modern is basically nil. Other than a handful of meta cards, most of those cards will be worthless for anything other than burning once they leave Modern.

I don't see any reason to make Chaos Legion more valuable than successive sets. Especially considering there are literally still hundreds of thousands of Chaos Legion cards to burn through. Stick with the plan.