Cordis Die supporters launch a massive global insurrection, resulting in the burning of the White House and widespread anarchy. This ending is canon and sets the stage for Call of Duty: Black Ops III.
In Black Ops II, Weaver doesn't physically appear in the campaign. Woods possibly references Weaver when stabbing Kravchenko in "Old Wounds", and telling him did he believe an eye for an eye. During the interrogation, he was either killed by Mason, or by Woods after he gave information.