Highly doubt current CAT8 cert will map to CAT8 in new program
Means Tier1-5 charts will be hugely devalued.
The way I see it, a direct porting of categories makes everybody below the Tier 4-5 Holders very happy as they can now redeem at more and better properties.
For Tier 4-5 holders, it is much the same.
The Certificate can still be used at any Marriott property they want PLUS they can now be redeemed at any top tier StR too.
I don't think this would be seen as a devaluation.
There is of course a scarcity question, with so many people then having access to rooms at top tier properties. However that falls more into the realm of a stealth devaluation and has far less of a headline risk, than the category numbers on certificates being marked down.