With thanks to Alison Brammer for pointing this out, the consultation currently open on the possible introduction of mandatory reporting of child abuse and neglect or a duty to act in relation to child abuse or neglect also seeks views in relation to the extension of such duties to vulnerable adults. The consultation is available here, and the deadline for response is 13 October.
Bear in mind that it may well be said at a later date that the Government has consulted upon such a duty in relation to vulnerable adults even though it is in the context of a consultation which looks (on its face) as if it has everything to do with children and nothing to do with adults…