User blog comment:Callofduty4/"blackops2" domain purchased by Activision/@comment-1646923-20120109223827/@comment-4478081-20120110031429

I suppose it's because everyone was expecting a sequel to CoD4 and MW2, so no one expected a different title. But with Black Ops, no one expects a sequel but instead a completely different title. They didn't exactly leave the story open for a sequel.