With a large BA back office presence in NCL, I cn't see NCL being dropped in the foreseeable future.
As to LBA, it was inherited from BMI. If it pulls its weight then it might survive, if not then it won't. Simple as.
All BA slots go into the 'maximise profit' matrix. With BA's LHR slot portfolio, there are no end of opportunties to expand longhaul. After all when you serve EDI, GLE, MAN, CDG, AMS, ABZ, ARN, BRU, CPH etc 8+ times per day, all you have to do is reduce each by 1 per day and you have longhaul growth when the aircraft arrive.
To me, there is no doubt that BA are slot sitting many of the ex-BMI (plus some BA rotations) until they have the airframes to convert them to longhaul. In that I include all the LBA, but not all the NCL rotations.