Hard to say without veering into the conspiratorial.
I think Activision makes calls that individual studies aren't always onboard with but you have to go along if under the umbrella for obvious reasons. I'm inclined to believe the two-year Duty was earnest but WZ 2.0 numbers weren't at all what they wanted so hot-potatoed the next instalment to Sledge as it's always worked in the past for yearly revenue vehicle.
If the rumors are true that it's a MWII sequel, man, that looks even sh*ttier, IMO, because it's a playerbase splitter and signals a house not in order. Have we ever gotten back to back Duties within one series? I don't think so. It reads plan-B desperate, TBH.