I`ve watched full Carmack`s keynote @ QuakeCon2011 and he was saying something like "maybe" or "possible".
Yes that's all. He said they might release such a patch but he mentioned only for a single level. And it's all a big "maybe".
But somehow this got interpreted as if id had just announced a high-resolution texture pack for the whole game that will definitely be released shortly after release and will be hundreds of GB big and so on and so the rumour spread....
But unfortunately no proof and until they really announce such a pack I wouldn't count on it
