Just seen this weeks White Dwarf and there's a new Warzone supplement book coming out for Apocalypse, detailing a conflict between the Eldar (and Dark Eldar joining in too) against the Tyranids of Hive Fleets Kraken and Leviathan (I think it's those two). I cannot remember the name of the book though, Koromar maybe, dunno. General plot seems to be a concerted effort by the Eldar to prevent the two Hive Fleets meeting/combining with each other in the wake of the attack on Iyanden. Nice to see an all Xenos 40k book for a change, here's hoping it sells well and maybe gives GW a nudge to produce some more.
There's a couple Apoc formations from the book in the new White Dwarf, one each for Eldar and Dark Eldar.
EDIT: The name of the book is Warzone: Valedor.