The host is actually hired by the Academy, and while ABC certainly has some influence over how the show goes, the Academy doesn’t have to listen.
Of course, just because ABC is ok with there not being a host doesn’t mean for certain that’s the way things will go.
The word is ABC was the force behind some of the recently proposed changes, like a new “popular film” Oscar, and while that idea was not implemented this year, it doesn’t mean it might not be incorporated in the future.