I've just seen a poster at Sydenham train station advertising the new timetable effective Dec 12th. It seems like a good set of changes: more evening trains, later night trains and very late trains on saturday evenings.
There don't seem to be any downsides (from my 3 minute scan of the poster) but I'm sure some STF'ers can find some negative smallprint
In addition there are two extra trains leaving New Cross Gate for London Bridge during the Mon-Sat off-peak, so you may be able to use the Overground to connect with those services if you miss our stopping services.
In addition, there is a later Overground service for New Cross Gate which connects with the final Southern service from London Bridge to Sydenham.
It's not perfect, but a start in getting later Overground services.