Census results don’t predict change; they just help to describe what has happened so far. The transformation of Northern Ireland to the point where Roman Catholics now outnumber Protestants has already occurred, and it is no longer the place I grew up in.
This represents the collapse of the political idea that prevailed after partition and is clung to hopelessly still; that the survival of the union depends on unionism being Protestant. Now there can no longer be a majority for staying in the UK that does not include Catholics. Any strategy for defending the union must appeal across sectarian lines.