The management can sack who they like - senior cabin crew? The first 50? Bassa reps?
Actually, I don't think they will sack anyone arbitrarily. I think they'll be able to find a few hotheads who will step out of line, against union instructions, and they'll be shown the door pretty sharpish and in a public manner. Staff travel will be stopped too for all in the short term, and with the threat of long term removal for strikers (precedent set in various other areas). The worst threat before the strike occurs, will be reserved for those who plan to call in sick. Pattern sickness will be the excuse that the company will use in order to suspend all those who are too scared/skint/reluctant to strike, but who are too scared of union retribution to go to work.
All in all, it will quickly turn nasty - people are used to BA being one of the most touchy feely companies in the UK to work for, and they'll get a shock when they see how they can be dealt with in the real world of big business.
Bassa seem to portray this strike as a risk free, cost free exercise. In reality, there's a lot of risk attached, and it's going to cost cabin crew dearly.