2Entertain have confirmed that Terror Of The Zygons, originally reported for release in 2012, no longer has a scheduled release date, but it definately won't be 2012
I don't understand why they are holding off so long on this story, especially given its popularity.
a) It's popular; b) It's one of the few remaining SJ stories unreleased (and definitely the best), and you'd think they'd take advantage of that; c) it was prominently referred to in NuWho, so easier to sell to fans who don't watch much classic. So obviously they're going to hold it back
They're probably busy with the 3D IMAX version of Vengeance on Varos