I've never overseen a merger before, let alone one of this scale, so pardon my blatant speculation... but will that really be such an issue?
It seems to me that the mismanagement of Acti/Blizz is a product of a corrupt corporate apparatus. From the inside of Acti/Blizz, the problem is basically intractible, but I don't think that really applies the same way once you install higher rungs of authority. MS is no stranger to acquisitions, either, so it's not as though they will be asleep at the wheel during this transition.
It may well be that he has a job in name in the new structure but not actually a role and after some discreet period he will be put out to pasture. Kind of sucks if you wanted him to receive some sort of cathartic day of reckoning but maybe a pragmatic solution.
The press release says they're keeping Kotick for the duration of the transition, then everyone will report to Phil Spencer. Seems likely that Kotick will be gone soon(ish)