The poster of the sensible rumors on 4chan added some details to what he previous said.
New stuff:
>Crawling Plague (named Venomthrope), Finecast
>- Like the other named tyranids is taken as a brood upgrade.
>- Three rows of vents on its back, tail is much longer and coils itself around a piece of scenery. Mouth tendrils are shorter and spread open around its mouth like it's trying to spit out something, with liquid dripping out of it.
>- Torrent weapon, AP- Poison 4+. Gimmick is on a 3+ place a marker anywhere on where you placed the template. Following turn place the small end of the flamer template on the marker and aim it in any direction, roll again on 4+ every subsequent turn to see if it stays on the field.
>- Grants stealth to all models within 6" and shrouding to itself. Venomthropes create 5+ cover, so they synergize.
>- It Lurks in the Mists: Special deployment gimmick instead of deploying on the board, at the start of any movement phase except the first you can deploy the Crawling Plague within 6" of any venomthrope.
>- Mutation from the new Hive Fleet Karkinos, which is specialized in toxic weaponry and the usage of venomthropes.
>Tyranid Prime, plastic clamshell
>- Larger Warrior, head crest has four prongs, additional shoulder plates that interlock down over part of the chest, armor in general is sharper and extends farther out with a slight upward curve. Looks like you could impale a guardsman on its back.
>- On foot, devourer and scything talons, dead easy to switch out components with Warriors and Raveners.
>- Details of the fluff are quite a bit different. The Prime is designed as a perfect hunter, created to fit any battlefield and seek out and eliminate enemy commanders while supported by evolved broods in this regard.
>- Apex Brood: The Prime can take a single retinue of "Apex" Warriors, Raveners or Shrikes. They receive T/WS/BS +1 and the Prime auto passes LOS! rolls while attached to the Apex Brood. Somewhat more expensive than their normal counterparts (+5 to +10 pt each depending on the creature)
>- No more +1WS/BS when attached to regular warriors, that's replaced by the retinue.
>- Hunter-Killer: Enemy characters cannot refuse challenges from the Prime.