Reading else where that CO have freed up a B764 in EWR yet to be decided where it will operate
Its more than likely going to replace a B767-200 route, given they are starting to phase these out.
If it was between MAN/DUB however, its hard to say. MAN-IAD starts ahead of DUB-IAD so possibility MAN could get and upgrade sooner, but without seeing the yields between MAN/DUB it is hard to call.