The Northern Ireland Office—as distinct from the 11 Northern Ireland Civil Service Departments—will be relatively unaffected by the restoration of devolution on 8 May, although there will be a reduction in the NIO ministerial team.
The eventual devolution of policing and justice functions will, of course, have a much greater impact on the size of the NIO. When that happens, the respective administrative funding streams attached to those functions will devolve with them.