Are all the new Shasvastii models going to be available separately from the defiance box? I kind of got the impression from the way the art is branded that they are Defiance models, compatible with infinity. As in they are in the defiance box.
According to Bostria nothings been finalised yet, we'll find out more when the campaign starts in October/November. Pretty much everything will be available retail after the KS (barring Preorder exclusive type things) but we're not sure in what form yet.
You might see a miniature only option in the KS campign. If there isn't one, I suspect they won't be sold separately.
So far it mostly looks like there will be both Defiance and Infinity models of various units. I think the only Shasvastii unit that's been shown as a Defiance render but not for Infinity is the Taigha Creatures.