Most of it is already leaked.
http://www.3plusplus.net/2014/05/7th-edition-rulebook-in-hand-live-post/Summary:
Landraiders will be around more.
Everything is scoring, so you'll see less troops and more elites/fast (heavy was always good).
Psykers took a huge hit. You'll see a lot less spells flinging about.
Assault based FMCs took a hit. Shooty FMCs got a buff.
Prescience went to 2 warp points, so cheap twin linking got a big nerf.
Invisibility is the new black.
D weapons taken down a rung (deservedly so).
Oh and Smash went to 1 attack. Poor Tyranids.
