Please remember that these are rumors and we always take them with a grain of salt. It does start to look like things are starting to align here.
August is Daemons wave (plastic troops, last two boxes)
Apart from CSM, no more codexes/Armybooks this year
I've heard talk about this wave possibly including something new... which presumably would have rules in WD ( or online ?) or somesuch.
A previous rumor via Stickmonkey
(from March 2012 http://natfka.blogspot.com/2012/03/chaos-daemon-whispers.html )
Hearing bits that aside from Plague Bearers, there may be new furies in the works. As well as seeing karanak and hounds of khorne moved to finecast soon.
Once we start looking at some of these rumors all together, it looks very much like furies could be coming with a White Dwarf addition, alongside some plague bearers, and on other box set I do not know off the top of my head this morning.