There are rumors that many of the new Greater Daemons are done and waiting to be released for Warhammer 40k. The recent models for the Endtimes have shown just how nice these new sculpts are, and if anything is released for 40k, I am sure a lot of people will be excited to hear it. This rumor states that the Great Unclean One may be coming in a month or so.
Please remember that this is a rumor. Hastings recently said that all the greater daemons are done.
via an anonymous source on Faeit 212
I got a good piece of news from a friend who works out of GW in Nottingham, He claims "new GUO coming in a month, maybe 6 weeks. Its a much much bigger model, posed in a similar fashion to the FW one but seems to have Nurglings spread around the base and guts. Theres some head variations too.