I personally think they will keep the 2 separate
Yep, I tend to agree. Perhaps CX will nick some of the better slots into Beijing and Shanghai to boost their services to the mainland. There might also be some tinkering to align schedules through HK, but I tend to think they'll leave the rest alone, for the time being at least. I guess they'll also 'rationalise' some management positions to cut-out any unnecessary duplication.