I arranged a tour around the Buckland Mill site last July for the River Dour Partnership, hosted by the developers and the Homes and Communities Agency. From what I can tell there is no need for DDC to invest in the site even if they could do or wanted to, it's a brilliant development and progress is going well but will inevitably be lead by demand.
Central Dover just doesn't have the space to build the size of house that is wanted by families, so high density housing is what will normally be built e.g. the post office social club site. Bigger family homes will have to built on the outskirts which means fewer facilities and access problems.