Soon, many releases will be getting new labels for 30k and 40k. The Horus Heresy becoming much more mainstreamed has been a topic here on Faeit 212 for a real long time. Squiggly has come in with the latest information on what we will be seeing regarding the Horus Heresy and the Betrayal of Calth releases.
Squilly is a very solid on his information. So take a look,
via Squiggly on Faeit 212
Basically the calth stuff will be released in boxes labelled for 30k and 40k. The HH range is a big thing, and a handful of kits is not a "big thing"
I know the Mechanicum models were intended to be Heresy models too. So I suspect they too will get repacked as 30k/40k models when the range is launched. Or soon after.
Yes the 40k Mechanicum stuff is all labelled the same, but it is split into two factions. They were intended to be one 40k faction and one 30k faction.
I hope that makes more sense.
"Previously on Faeit 212" in a deep announcer voice
http://natfka.blogspot.com/2016/02/horus-heresy-range-about-to-expand.html
HH range should kick off in the spring. April-May time. As you already know the Calth stuff will kickstart the range, with boxes labelled for 30k and 40k.
The plastic Mechanicum stuff was intended to work over as part of the core Heresy too.
So I suspect the Mechanicum stuff will get a repack alongside the Heresy releases, when they're released this spring. as the Mechanicum range. Rather than Cult Mech. and Skitarri. The Calth kits aren't exactly a "range" on there own.