After answering a question in SciFi if the Big Brother existed as a real person, I got responses that the last chapter, the Appendix (which can be found here), definitely proves that Oceania ceased to exist because it describes Newspeak from a historical perspective. One proponent cited an essay to put the argument forward.
As a non-native speaker and unsure about the exact usage of English, especially during the time the novel was written, I would like to ask if the argument is correct.
First I find the usage of the word "Appendix" strange which indicates normally a technical description outside the given text. The whole text sounds for me more like Orwell had worked out the technicalities of the Newspeak, but could not find a place in the novel where it really fits. Second I believe to remember that several old German books used past tense in descriptions, so I wonder if this might have been used in WWII English, too.
Does the text (especially "Newspeak was the official language of Oceania and had been devised to meet the ideological needs of Ingsoc, or English Socialism") in the Appendix definitely and unambigously prove that
a) the Appendix really belongs to the story and
b) Oceania ceased to exist in the future of 1984 ?
Further clarifications are welcome.