I can see the overall pay package being slightly better than the current new entrants' package. It will likely involve a fairly significant hourly rate (incentive pay), and will also include incentive pay during holiday periods too. BA will save significant money by getting cabin crew holiday pay sorted out before the pilots win the last holiday pay entitlement tribunal appeal. A bidding system will also lessen sickness, whilst increasing efficiency with the mixed fleet. Overall, it is going to be good for the majority of cabin crew, whilst at the same time saving BA quite a considerable sum.
Note that none of this is based on known fact. It is all just my best guess.