Isn't that line about a foot stomping on a human face forever a quote from O'Brian? If so, it's the kind of thing he'd like to believe, but it wouldn't be the sort of thing that could be known, and is less likely to be accurate considering that atmosphere of lies that Oceania had.
On the other hand, I wouldn't be surprised if Orwell meant it to be taken straight.
Second thought: O'Brian might not have believed it himself (what does belief mean to an Inner Party member?), he just might have been saying it to get Winston to despair.
One of the other implausibilities of the book is that people who get hurt in dictatorships are generally just ground up by the system, they aren't targeted by a highly intellectual stalker.
And Margaret Atwood made this point:
But this view of Orwell is contradicted by the last chapter in the book, an essay on Newspeak [..] the essay on Newspeak is written in standard English, in the third person, and in the past tense, which can only mean that the regime has fallen, and that language and individuality have survived. For whoever has written the essay on Newspeak, the world of Nineteen Eighty-Four is over. Thus, it's my view that Orwell had much more faith in the resilience of the human spirit than he's usually been given credit for.
Orwell's Nineteen Eighty-Four is brilliant, terrifying and useful. It's been at its best fighting against governmental intrusions, and is often quoted by journalists and even judges. It's cultural impact has been immense. And, hey, it's well written.
But that doesn't mean it's accurate as a source of predictions or counterfactuals. Orwell's belief that "British democracy as it existed before 1939 would not survive the war" was wrong. Nineteen Eighty-Four did not predict the future course of communism. There is no evidence that anything like the world he envisaged could (or will) happen. Which isn't the same as saying that it couldn't, but we do require some evidence before accepting Orwell's world as realistic.
Yet from this book, a lot of implicit assumptions have seeped into our consciousness. The most important one (shared with many other dystopian novels) is that dictatorships are stable forms of government. Note the "forever" in the quote above - the society Orwell warned about would never change, never improve, never transform. In several conversations (about future governments, for instance), I've heard - and made - the argument that a dictatorship was inevitable, because it's an absorbing state. Democracies can come become dictatorships, but dictatorships (barring revolutions) will endure for good. And so the idea is that if revolutions become impossible (because of ubiquitous surveillance, for instance), then we're stuck with Big Brother for life, and for our children's children'c children's lives.
But thinking about this in the context of history, this doesn't seem credible. The most stable forms of government are democracies and monarchies; nothing else endures that long. And laying revolutions aside, there have been plenty of examples of even quite nasty governments improving themselves. Robespierre was deposed from within his own government - and so the Terror, for all its bloodshed, didn't even last a full year. The worse excesses of Stalinism ended with Stalin. Gorbachev voluntarily opened up his regime (to a certain extent). Mao would excoriate the China of today. Britain's leaders in the 19th and 20th century gradually opened up the franchise, without ever coming close to being deposed by force of arms. The dictatorships of Latin America have mostly fallen to democracies (though revolutions played a larger role there). Looking over the course of recent history, I see very little evidence the dictatorships have much lasting power at all - or that they are incapable of drastic internal change and even improvements.
Now, caveats abound. The future won't be like the past - maybe an Orwellian dictatorship will become possible with advanced surveillance technologies. Maybe a world government won't see any neighbouring government doing a better job, and feel compelled to match it by improving lot of its citizens. Maybe the threat of revolution remains necessary, even if revolts don't actually happen.
Still, we should refrain from assuming that dictatorships, whether party or individual, are somehow the default state, and conduct a much more evidence-based analysis of the matter.