I can't seem to find anything to support this but my MIL said it was in the news last week that the World Health Organisation had admitted they'd made a mistake on the wean at 6 months advice and that parents were being told to go back to the 'traditional' weaning age of 4 months.
I asked whether she meant the independent study that hit the press in January but she said it was definately the WHO and they were admitting they'd made a mistake.
My youngest is nearly 1 now so it's all academic really but I'd be very interested to know.