It should be grandfathered across but of course that would be too simple for our CAA.
The UK CAA has no say in the matter; the decision has been taken elsewhere in Europe, predominantly by bureaucrats and lawyers, and will be imposed by EU law. Like so much of the cr@p that comes out of Europe, there is no safety case to support it, no logical justification for its introduction and no right of appeal against it. Welcome to the brave new world.