Yesterday in the rumor mill, Stickmonkey is letting go of what models we should expect for 2013 for both Eldar and Orks. In the works there is mention of a couple new units not seen before for 40k, including a new Eldar Tank, New Eldar bomber, and more.
Please remember that these are rumors.
via Stickmonkey from Bols
Eldar Miniatures (alongside the codex)
Farseer
2 Aspect Characters
2 other characters (Either HQs or Unit Upgrade characters)
New Aspect (plastic)
Wraithguard (plastic)
New Eldar tank
New Eldar Bomber
Eldar Miniatures (outside the codex)
New Flyer
Guardian Jetbikes - Shining Spears combo-box
2 existing Aspects moved to plastic
Avatar (new model, bigger than a Dreadnought)
Warp Gate (Terrain kit)
Ork Miniatures (alongside the codex)
New Weirdboy
Wazdakka
MegaNobs - Tellyportas combo-kit
CybOrks
Grot Gliders - (very odd one, a 40K version of WFB Doomdivers?)
Mega Mork/Gork - (your guess is as good as mine)
Ork Miniatures (outside the codex)
New Buggy - Half-track
DeffCoptas
Flashgits - Tankbustas plastic combo-kit