Book seems slated for a Feb/March release, written by Jeremy Vetock and apparently already done! (strongly hinted at by hastings and harry, and also seems in line with the known release schedule)
We keep all current SC(that includes Grom in his chariot!) and get Wurzzag and two goblin characters both heroes one of which is a forrest gobling for a totalt of 15 lord choices and 11 hero choices!
We get a new model, the Arachnarok spider. It can be takes as a mount for a common gobling great shaman, or it can be a rare choice. As a rare choice it will have options for some warmachine thingie 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. (I am still a bit unclear whether the upgrade is the new Special Char or a seperate upgrade like the DE assasin)
(Common) Goblin characters will be able to ride Giant and Gigantic spiders, so an all spider army should be viable (hastings).
Also we are getting another new unit besides the Arachnarok, though it is unclear what it is at the moment.
We get some new plastics, so far people agree on we get 5 sets:
Besides the spider, the best bets so far are Savage Orcs incl boars, with the remaining two to be named. One which could be the new as of yet missing unit.
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
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.