Yup, they are! Like I wrote before they did the same thing with chaos dwarves. You get a box of regular dwarves plastic sprues + tons of metal bits to convert them into evul dwarves. Suprisingly, it works pretty well, and I'm guessing it's much cheaper then releasing brand new models, and Mantic seems to try to save money whenever they can, presumably so they are able to keep their competetive prices.
Funny thing is they've have released a test batch of these twilight kin, I think 10 army sets or so. You could buy them during Mantic's open day and there was one or two in their online store. They're all sold out by now though.