next codex release

After blood angels, what is the next codex planned to be released by GW?

Grey Knights most likely. There have been sightings of the 3-ups for plastic terminators and marines, and they will apparently get the storm-raven as well, allowing this major vehicle for the BA to be released.
DE and Necrons still fighting for end year, but I doubt anything until January, as GW usually drops 3 codex's a year on average.

Most of the rumors I have seen tend towards DE, then Necrons, with A combined Inquisition codex slotted for 2011.

However, one has to remember that Codex rumors are almost all entirely opinion-based. Nobody really ha any clue except GW. And even if they provided honest leaks, said leaks would still be over-whelmed by the huge amounts of s**t-rumours on the good ol' interwebz.

Some useful links:

Inquisition Rumour Compilation Thread (courtesy Heresy-Online): http://www.heresy-online.net/forums/showthread.php?t=55212

Dark Eldar & Necron Rumor Threads:
http://www.heresy-online.net/forums/showthread.php?t=57214
http://www.heresy-online.net/forums/showthread.php?t=35582

I trust in Harry from Warseer. He has been right 100% of the time for Rumors. he cryptically said earlier this year that after blood angels, another Astartes force would be "winging" its way in. Some people thought Dark angels, and he said "think Shinier". Now, with the confirmed sightings of GK 3-ups being shown at warhammer world, I can't see DE coming out before the knights. It seems though, that inquisitors may really be reduced in this 'dex, marginalized over the Knights themselves.

I have tended to steer clear of Warseer, personally, but that is just a preference thing more than anything. So far, the rumor mill on Heresy has been smack-on as well.

Truth be told, though, we likely won't be seeing a new 40K codex until the sumer at least, if not later. What with Spearhead coming out in June, and I do believe they are doing a new version for Warhammer Fantasy Battles this year as well.

ya they are this will probobly be more of a wfb year

I think everyone's getting hasty, as much as I would like to see a new necron's dex it's about as likely as a new season of firefly. The next dex is mostly likely not going to be released until late this year (the last 12 months has already seen an unprecedented amount of new codex's, not seen since the release of 3rd edition) More likely than not the next dex is a space marines dex because we're not sick of them yet right? it's not like we've all heard enough blood angels rumours to puke blood already...

My vote is next space maines (any flavour they all taste like =I=censor=I= anyways) then chaos space marines early 2011.

I look forward to being pleasantly surprised.