That might just be the twitter team's way of saying there's 5 diagrams left, although I would be surprised if they keep 8 units to cover 5 diagrams right through until December.
I would be equally surprised if they get the full compliment of 385s in advance of December that they would leave them lying around spare whilst the last 314s rattled away.
It is possible though - I think they have a headache regarding what to do with the Neilston peak services. I'm not sure there's enough class 318/320s to form 2x6 car workings currently worked by 314s, and 380/385 are restricted to single units due to the turnback, so running the 314s longer buys some time to deal with that. It might need a bit of a diagram/timetable recast if they don't want to remodel the station.
Can anyone confirm 385s are cleared and if any or on neilston services?