I'd miss it but think it's probably time to call it a day. Several characters seem to have run their course. Sr Julienne has come across as bored and fed up at Nonnatus House over the past couple of series, Trixie looks out of place and like someone who desperately needs to move on, and Phyllis is obviously approaching retirement age and now has the financial means to do so.
Poplar would also have been rapidly changing by the late sixties. Most women would have been having their babies in hospital and a welfare state would have been running a lot of the services traditionally supplied by the sisters. The demolishment of the old tenements would have altered the feel of a community once populated by families who had known each other for generations. A huge migration out to the newer suburbs, particularly by younger people would have been another radical change.
Probably time to give Trixie her happy ending, retire Sr Monica Joan to the mother House, let Cyril and Lucille buy a house somewhere and start a family and, presuming Sr Julienne has died in the crash, charge Sr Hilda with guiding Nonnatus House into a new and different future.