If he'd have lived longer, he might (according to his friend and critic TR Fyvel) have become a little passé. Don't get me wrong, one of my favourite writers, but his time was undoubtedly the 30s and 40s, not further on. Even at the time, 1984 harked back to an age already passed; a bombed-out London reminiscent of the Blitz, Fascist/Communist tendencies within British society etc, were all drawing on themes he'd explored in previous essays. Even Winston Smith's conversation with an old 'working class' man on one of his trips out sounds really like the speech he heard amongst tramps in Down and Out in Paris and London. Orwell by the time of his death was certainly a great writer, but as for the themes of his works, they were stuck in the past, and I highly doubt that after 1950 we'd see any of his writings get any more popular upon the strength of their own merit (rather, 'Orwell was rather good with 1984 wasn't he...and look, he's got another one out on the shelves, might as well buy that').
1984 remains as pertinent today as it did when Totalitarian regimes ran rampart in Europe. I don't think its message will ever get weaker even as time goes on and the world continues to democratize.