In 1984, could O'Brien be vaporized in the future?
When I was reading 1984, the fact that Syme was vaporized, presumably for exhibiting independent, deep, intelligent thought, raised the issue in my mind that O'Brien, although an orthodox, and somewhat fanatical supporter of Ingsoc, displays similar traits to Syme in that he does not simply support the Party and BB out of blindness or a primitive sheep mentality, but, like Syme, has clear opinions and understands the ideology of the Party, as a result of his intelligence. Further showing his unique character and mental unorthodoxy is the fact that he likens his own mind to Winston's. Seeing as the two characters his person can be related to the most are both vaporized for "crimethought," is it conceivable that O'Brien himself, because of his intellectual capacity and clever thoughts, could himself be vaporized by the Thought Police at some point in his life?
This is a very interesting idea to think about, and you might benefit from moving this question to the discussion board of this group where you would get many more responses. However, just initially, Winston Smith is not vapourised as we assume Syme is. Smith is broken, completely and utterly, by O'Brien.
Let us remember though when we consider this question that the model for this world, Stalin's Russia, was one that was famed for its purges. A key aspect of this was the way that those involved in leading the purges (which were responsible for the deaths of millions of Russians) were themselves victims of later purges. Stalin was notoriously paranoid, which could perhaps explain this. However, the society in 1984 is one which denies safety to all of its citizens, and therefore I think you are right in thinking that O'Brien at least has the potential to be purged later on in the world of this novel.