Isn't it one of the possible destinations for an extended Bakerloo line?
And the DLR. And the Tramlink. There have been many suggestions, many of which have merit but I think LR did a study and 'do nothing', as often, was the reco.
Bakerloo is out - seems most likely to run to Hayes (possibly with a spur to Beckenham Junction, which I like) and Grove Park layout would be too difficult.
DLR I can't see running south of Lewisham, and especially if the Bakerloo runs to Catford (Bridge) - is duplicative. And tons of development in Lewisham would make this near impossible.
That leaves the Tramlink, likely from Beckenham Junction down into Bromley town centre and swoop back up - terminating at Grove Park.
Is this useful though? It retains the Grove Park link per today (likely at higher frequency), removes a slight complexity of the shuttles, it covers off Beckenham and Croydon to Bromley routing (potentially all the way to Wimbledon if planned, and presented as a southern orbital). It integrates into an existing mode, with plenty of new combinations and pairs - the one downfall is not linking into the many Kent services at Bromley South.
And it likely would boost the Bakerloo spur to Beckenham itself, in purpose and as a hub.