Okies, I am relatively new to 40K; ::grin:: only since halfway thru 5th as a functioning player. But my understanding is that the Squats were aliens, basically Space Dwarves, mildly cartoonish in portrayal, from Fourth edition or earlier, and that they were utterly discontinued, and then not referred to, ever, in official GW anything.
Welp, if you will take your brand spanking new 6th ed book (standard one, I dunno if the limited edition ones have a different layout) on page four-oh-four (this is in the appendices) you will find the section on abhumans. On page four-of-five, fisrt column, second paragraph, the Squats are listed as a not-extinct stable variety of abhuman.
Troths, Felinids, and Neandors are apparently highly limited; Beastmen are well on the way to being declared as mutants, with all the relevant bad things applicable to that status within the Imperium. But the section concludes with "The remaining abhuman races are variously present across the entire Imperium. In some regions they are plentiful and common, living in large colonies or even populating entire worlds, in others they are scarce and virtually unknown." As I read this, it would strongly imply the Squats are once again canon, and the 'Nids did not, in fact, eat them all. Which would explain why the 'Nids are getting bigger, and not smaller.
By the way, who or what are the Troths, Felinids, and Neandors? From the name, I would expect Felinids to be Cat-folk, but what are the others?