Here are some of the new units available (rules where known):
Etheral - a psycher, who has a staff which has rules similar to Tyranid Rending Claws.
Hammer Head Grav Tank - armed with a S 9, AP 3, Heavy 3 railgun. Can deploy heavy weapons on the battle-field.
Devilfish Grav APC - ??
Pathfinders - 5+ saves
Basic Troopers - 4+ saves. Their basic weapon is a pulse rifle (S 5, AP 5, rapid fire)
Fire Castes - 3+ saves and jump packs (assault troops)
Kroot Ox - a large gorilla-like creature, with a Kroot on the back carrying a weapon
Kroot Hound - ??
Kroot Carnivores - ??
One rule they are supposed to have is that if they break an opponent they must pass a leadership test or they will start eating the corpses of their enemies!
The boxed army set and codex are planned to be released in October / Semptember, around the time of Games Day. The box will cost £100 like the other armies. Interestingly, there is also talk of a re-release of 40k around then, with a book of updates compiled from Chapter Approved in the White Dwarf magazine. Another 'starter' boxed set will be available with Space Marines and Tau in it.