I'd really like to see the Slaugth detailed further in Rogue Trader. I've found them to be a versatile menace for my players, both as straight up monsters and as the backbone of the Amaranthine Syndicate.
What little there is written about them mentions that they may have an empire hidden somewhere in the Halo Stars. There's also a bit about their "tenebrous vessels" in the GM's Kit booklet. I'd like to see the stats for these, and more on their technology as well.
Anyone else hoping to see the Slaugth or any of the other races expanded upon?