According to this site.... (a516Digital)
"A number of BBC local radio stations will cease broadcasting on Medium Wave."

The piece goes on to say that several stations- where there is sufficient FM or DAB coverage -will loose their AM service from January 2018.

This follows a successful trial when there was little public reaction to the closure of their local station's AM service.

The BBC Local Radio Stations involved are:-
Sussex, Surrey, Humberside, Wiltshire, Nottingham, Kent, and Lincolnshire which will no longer broadcast on AM, and  BBC Devon, Lancashire and Essex will have reduced AM coverage.

In his BBC blog, here, Kieran Clifton (Director, BBC Ditribution & Business Development) says that 13 Medium Wave transmitters will be closed in 2018.