via Tyran on Dakka Dakka
I just have a nice chat with a player in Vassal.
He supposedly got to see the new codex in a veterans tour at Warhammer World.

Rumors:
Tyranids can't take fortifications, but have +1 HQ, +1 Elites, +2 Troops, +1FA and +1 HS
Tyranids are going to have 3 supplements: Leviathan, Kraken, and Jormungandr. It is going to be a swarmy one, a nydzilla one and an infiltration one. But GW hasn't started to write them yet so anything may come.
There are advanced, basic, experimental, etc biomorphs.
Shadow in the Warp is a 12" bubble of -4 ld for enemy psych test, but also grants units the 5+ to deny.
No way to make Warriors viable, according to him the Eternal Warrior rumors are wrong.
Toxins Sacs may be the same, according to him the wording was poison 4+ to the attacks, not making any distinction between CC and ranged.

Flesh Hooks are assault grenades and d6 S6 ap5 rending and precision shoots.
Adrenals Glands give Furious Charge and the +3" run.
Scything Talons give an additional attack.
No Doom of Malan'tai, Parasite and Mycetic Spores.
Regeneration gives IWND.
Catalyst gives +1 to FNP and IWND.
Venom Cannon is S9 ap4 2 shots.
Deathspitter is back to being a blast.
Barbed Strangler is st6 ap5 and must take a S test or take d6 st4 ap3 hits.
Stranglethorn Cannon is the same but S8 and pinning.
Acid, explosive and poison spore mines are back.
Any Prime unit can be HQ, this includes Warrior Prime, Trygon Prime and Old One Eye.
Only 1 Psych Powers chart.

Carnifex:
120 points
Got a new page of upgrades.
2+ save for 15 points
1d3 Hammer of Wrath attacks
Can attack the occupants of a transport after destroying it in CC.

Harpy:
140 points
Fast Attack unit
WS 4 BS 3 S 7 T 5 W 4 I 5 A 3 LD 8 sv 4+
Sonic Shriek is when it flies over unit.
Also carries spore mines
Born in the Skies: Can't be grounded

Crone:
170 points
Fast Attack unit
WS 3 BS 3 S 8 T 5 W 5 I 5 A 3 LD 8 sv 3+
4 S7 ap2 shoots or 1 S7 ap2 large blast
Missiles
Born in the Skies: Can't be grounded

"Haruspex":
Elite unit
"Magna Graple" attack
WS 4 BS 3 S 8(or 9, he wasn't sure) T 6 W 5 I 4 A 5 LD 8 sv 3+

"Exocrine":
Heavy Support unit
3 S10 ap3 shoots or 1 S10 ap2 large blast ordnance
WS 4 BS 3 S 8(or 9, he wasn't sure) T 6 W 5 I 4 A 3 LD 8 sv 3+

Tyrannofex:
180 points
Rupture Cannon cost 20 points

Old One Eye:
300 points
It is an upgrade for a Carnifex brood, but it also can be an HQ option
4+ IWND
3+ FNP
2+ Save


Hive Tyrant:
160 points
BS4
Wings for 30 points
Mastery Level 2

Tervigon:
170 points
Mastery Level 2
Can take 1 of 3 upgrades for spawn: 4d6 spawn, or the no run out for doubles, or all gaunts (note that it includes Termas, Hormas and Gargoyles) benefit from Toxin sacs and Adrenal Glands
Also you can customize the spawn options for a cost, for example spawning hormagaunts or spinegaunts

Lictor:
Shrouded and Stealth
Doesn't scatter

Deathleaper:
All attacks are precision
Keeps the 5+ rending

Trygon:
6+2 (from Scything Talons) attacks, Initiative 5, WS 5
Bio electric field: 6 S6 ap5 shoots or a 5++ invulnerable save

Trygon Prime:
Gaping Maw experimental biomorph: If half or more of the attacks hit, a random model in b2b takes an Initiative test, if fails it is removed from play. According to him it has no limitations, so it can eliminate a Riptide or anything else.

Mawlocs:
140 points
1d3 blast with the ignores cover rule for its attack from below

Tyrant Guard:
Broods of 1-5
Lots of options

Hive Guard:
New gun is Spike Cannon, S7 ap4 2 shoots with Skyfire, enemy must reroll successful grounding tests

Gargoyles:
5 points
Fast Attack unit
Lost Blinding Venom

Hormagaunts:
5 points
Bounding Leap is charge after running
.
Swarmlord:
Mastery Level 3

Zoanthropes:
Mastery level 1, but generates 2 warp charges (for Warp Blast)

Venomthropes;
30 points:
Grants shrouded and defensive grenades in a 6" radius

1) There is a known 40k photoshop faker on 4chan (the Steel Legion hoax)
2) The image used in that cover is available from the GW Tyranid codex iTunes store
3) "Iyanden" is not aligned with "The Battle For"
4) We have word of "Battle For Macragge" as the Tyranid based warzone book.
5) A plastic Hierophant? The design studio shies away from just ripping existing FW models in plastic.
6) Title font graphic treatment is different from past Warzone books (look at the Pandorax/Damnos cover below)