Agreed, given that this is fiction, everything is possible, however... ... since this is an in-universe account of Newspeak (because of the way the essay refer

Agreed, given that this is fiction, everything is possible, however... ... since this is an in-universe account of Newspeak (because of the way the essay refers to Newspeak, we know it's not just Orwell the author speaking), and since this account wouldn't be possible in Newspeak itself, and furthermore, and because this is written in past tense, we have a pretty good indication that Newspeak failed. And because Newspeak and Ingsoc are irrevocably married, we also have a good indication that Ingsoc itself must have failed. This is a coda explaining in-universe some details of a failed regime, much like the similar one at the end of The Handmaid's Tale (though that one is way more explicit).