They won't necessarily go anywhere. They don't need a similar card. After a certain point the annual fee becomes less and less worth it as does using the card for transactions. If it was this easy for them to devalue in quick succession then we would've seen them devalue a lot more a long time ago.
The other cards don't really have much in the way of international transfer partners as it is. Also the nature of the devaluation depends on whether there's a carve out for premium cards as mooted above. If there is then we might not see much of one.
Michelle Bullock sounded very defiant a few months ago on this but now suddenly has been forced to delay things.
