I'm assuming that the RC-135 will replace the Nimrod in a surveillance capacity.
However the Nimrod also did ASW work and I haven't heard what will take on that role. Helicopters don't have the range, endurance or payload to cover the same area as the Nimrod.
I read on the BBC website yesterday that some idiot claimed NATO no longer needed aircraft that could do long range ASW in the Atlantic.
Don't these people know anything?
I suggest they read up on a conflict called 'World War 2' with special attention to the section marked 'War in the Atlantic'