Bad Dog said:
I almost guarantee we won't ever see Tanith. For one, First and Only. They -are- the only regiment from there, the first regiment ever founded from there.
Second: We haven't seen the Iron Snakes yet. Another Abnett Creation. The copyright probably won't allow it. Things get complicated between IPs like that (It's the same reason we won't ever see the Blood Ravens - they're owned in part by another company that isn't GW, so FFG would have to negotiate a license to use it with them too)
Actually the Iron Snakes have been mentioned officially in Deathwatch - there are stats for power spears for them. As such Abnett's IP is a-okay for usage.
By the later novels in the First-and-Only line, the regiment has taken heavy casualties but also merged with several other sets of troops. I see no issue with a platoon of Tanith being seconded to a heavy infantry or armour force as a scout detachment. Seems entirely viable to include them in the book, even if not statted up at least as an honourable mention under light infantry.
So, when you say this, are you sure it is a specific weapon, for specific people? Having a spear-format power weapon isn't the same as having a particularly picked weapon, listed as for a specific group, who don't happen to be Space Marines. If you have a page number, I would like very much to go see it, as I often like non-Space Marine things in DW; while they are the focus, it's nice to see a few little things for everyone else fighting in their war.
As for one IP allowing the use of others, even if they did get permission to use Abnett's stuff in one spot, that doesn't necessarily open the door for his other stuff; he has to agree to every little one. Luckily, a willingness to allow it, in a 40K official work, such as their RPG, does reflect, at least to me, a willingness to probably allow more, again, if only to get his stuff some more recognition, which might drum up some book sales for him.
If i get stuff for Cadians (almost a given), Elysians, and maybe some unique to the works Regiment, I'll be pleased enough. If they just say "Guardsmen are Guardsmen, all across the galaxy", and then give us some flavor packages to flesh them out, as a specific group, so that the Cadians and the Catechans are not the same, that'll work for me.