The Tyranid codex release had a couple units in it that were not longer available from its previous incarnations. The most dramatic of these was the loss of the Mycetic Spore Pods. Today's rumor address's this and hits the nail on the head on what is going to be happening in the near future.
Please remember that these are rumors. This rumor in particular comes from a long time respected source on the site.
via an anonymous source on Faeit 212
Mycetic spores and some other choice tyranid units will see a return via Forgeworld alongside downloadable rules intended for use in standard 40k games.
