The new O&G book is confirmed for March 2011, see the GW Incoming! article.
Pre-orders will be up at February the 9th. With releases the 5th and 13th of March. It is yet unclear what will be released when.
According to Harry, "in 8th edition, and starting with Orcs and Goblins we can expect a whole different kind of army book. Obviously many of the same sections will be there but expect something a bit different." The army book is rumoured to be hardcover, and to be a good bit bigger than the current one.
We get 3 new plastic sets and 3 new blisters:
Plastic:
* Savage Orc Boyz
* Savage Orc Boar Boys
* the Aracharok Spider
Blister:
* Wurrzag on foot
* Savage Orc Great shaman on boar - He is repudetedly standing on the boar and the boar is a metal version of the new boars with slightly bigger horns and some savage orc adornements (feather/bone)
* a third blister of (yet) unknown content
Things we do not get:
* Orcs do NOT get devestating charge (hastings).
* Hobgoblins.
* common forrest goblins (on foot).
* Orc Idols and some huge cave beast (though we might hope Warhammer Forge may come up with something nice, eh? But nothing is in the pipelines just yet according to people that talked to them at Games Day UK)
* Plastic Sguigs
* Black Orc Boar Boys
* Skirmishing giant spider riders
* new common Goblins on foot and wolf
* new Boyz on foot
For a future wave release, there might be new common goblins and wolf riders in the pipeline.
We keep all current special characters(that includes Grom in his chariot!) and get Wurzzag and two goblin special characters; both heroes, one of which is a forest goblin on a giant spider (aka cavalry base spider) for a total of 15 lord choices and 11 hero choices!
We get a new model, the Arachnarok spider. It can be taken as a mount for a common goblin great shaman, or it can be a rare choice. As a rare choice it will have options for some warmachine thing or other special rule in that regard.
Common goblins will get some sort of a unit upgrade. Hastings hinted at something that has two handweapons but is not an assasin.
(Common) Goblin characters will be able to ride Giant and Gigantic spiders, so an all spider army should be viable (by Hastings).
Also we may be getting another new unit besides the Arachnarok, though it is unclear what it is at the moment.
Courtesy of many of these rumours to Hastings. Thanks also to Harry. A big thank you to Ney, for updating the last rumour thread on this topic.