So we didn't see Harlequins coming - sneaky Eldar, but we might start predicting the next codex. If you take a peek on the GW webstore you will spot lots of sisters of battle out of stock. Given that GW have long since abandoned Metal and Finecast is being phased out, we can deduce that they are busy casting new plastic kits for this army - and that can only mean a codex for V7 40K and some juicy new stuff to go with it. I predict an early April release, but who knows with GW?
There are also several Dark Eldar finecast models out of stock, the Grotesque and Slythh in partiular - so there could also be some new plastic kits for the court of the Archon and Grotesque units - possibly as a delaying release to the sisters - keeping people on their toes and me happy too as i would rather these over sisters.
Keep your eyes peeled - you may spot some new releases yourself. Seek and ye shall find.