Taken from Warseer
General info
Release 16 January 2010
Written by Robin Cruddace (author of IG Codex) and is 96 pages long.
Phil Kelly has also said we can expect to see "4 new species never seen before in a codex, one dwarfing the Carnifex." Most solid sources agree this large species is likely the Trygon.
The Incoming Tyranids article on the GW website makes mention of new Tyranid Species.
Codex Cover – Art by Adrian Smith
http://www.warseer.com/forums/attachment.php?attachmentid=71029&d=1254136277
Box art background:

http://www.warseer.com/forums/attachment.php?attachmentid=71509&d=1254475533
http://www.warseer.com/forums/attachment.php?attachmentid=71508&d=1254475499
Studio army will be in Hive Fleet Leviathan painting scheme with red weapons (as on cover and new box art).
A full summary list has been posted on the internet, but it includes far too many large creatures and has been generally dismissed as fake or wishlisting.