I would expect that you could buy the DA box until the main Codex release.
I was thinking aswell, that we haven't seen anything of Jetbikes or the rumoured Guardian double box, along with the plastic aspects. But seeing as we know that there is a Craftworld Iyanden companion book, and the units being released favour that configuration of army, could we see Jetbikes when Saim Hann is released, and Guardians with Ulthwé? Leaving the Aspects to be split between Alaitoc and Beil Tan?
Failing that, these supplements could just creep out as a foot note for the next few months.