It is certainly arguable that civilization (if that is quite the word) has reached the point described by O'Brien at several times and in several places throughout human history. O'Brien is right to point out that the ability of a totalitarian state to control its subjects is continually increasing, so that the Party will not fail in the same way as the Spanish Inquisition. This is why the societies that most closely resemble the one Orwell describes, and the one he has O'Brien describe in the future, are all either current or fairly recent.
The most obvious current example is North Korea, where the Great Leader, Kim Il-sung, and the Dear Leader, Kim Jong-il, both dead, are widely regarded as immortal, and as possessing superhuman powers. In an interesting piece of doublethink, when Kim Jong-il died, North Korean propaganda simultaneously stated that he was not really dead and that universal nature was lamenting his death, so the birds stopped singing and all the animals in North Korea went into mourning.
Of course, we have no way of knowing how many North Koreans actually believe what their government tells them. However, given that brain scans grow more accurate all the time, as does our understanding of how the different parts of the brain operate (and so can be damaged or manipulated), there is no theoretical reason why a totalitarian dictatorship such as North Korea might not turn into exactly the type of society O'Brien describes in the fairly near future.