The police will obviously examine any evidence that is presented to them, and if they think there's enough to charge anyone the CPS will make a decision.
One of the great difficulties with child abuse cases lies in getting victims to come forward and give evidence in court. As time goes on many victims would rather just leave the past in the past.
The allegations you refer to are just that at the moment - nobody really knows quite what is supposed to have happened and when. It looks as though a vital dossier containing evidence, or references to evidence is missing, and it may take a government inquiry to move things forward.