A little on it from Harry:
Sculpts have been around for about 18 months. (and well worth a bit of saliva )
I honestly don't know the order they will appear ...
.... but if it helps, the order that I heard about them was: Grey Knights, Sisters, Black Templar.
Whilst I expect them to appear in this order .... This was a couple of years ago so anything could have happened in the development stages before release order was set in stone.
(Lord Castellan is a braver man than I ... I certainly would not be risking my todger on the table with a guarantee of anything!)