There have been several studies on the stretch from St Dunstan's to Plassy Road island as something needs to be done. TfL has said one day but not now and no money for about 40 years by my reckoning.
The original Catford Plan would have used the land currently reserved for rerouting of south circular (on Plassy Road, council car park, etc) hence TfL suddenly got a rocket up their rears and are now supposedly seriously looking into what to do with the south circular.

The solution around the centre of Catford should be relatively simple. The main problem is the railway bridge and river. It could be solved just would be rather expensive and as anyone who looked at TfLs grand review earlier in the year south east London just is not a priority. To date. The TfL study is at least 6 months overdue from when initially promised so wish some update would be given. Then Lewisham can get on with sorting out the Catford centre. As long as they keep the cat.