We have indeed been putting Lovecraftian monsters in our Bestiaries from the start, along with some other creatures from public domain literature—we generally provide a partial list of these monsters in the first paragraph of each Bestiary's introduction:
Bestiary 1: H. G. Wells's morlocks, Lovecraft's ghasts and shoggoths
Bestiary 2: Frank Belknap Long's hounds of Tindalos, Lewis Carroll's jabberwock, and Lovecraft's Leng spiders, gugs, denizens of Leng, and shantaks.
Bestiary 3: Lovecraft's moon-beasts, vooniths, yithians, and zoogs; Lewis Carroll's bandersnatch and jubjub bird—also Robert E. Howard's zuvembie and China Mieville's ceratioidi (although those last two are unusual cases and aren't from the public domain—we got permission from Howard's estate to print the zuvembie and hired China to develop the ceratioidi for us in "Guide to the River Kingdoms")
Beyond this, we often include mythos elements in our adventures—Pathfinder AP volumes #4, #6, #21, #49, and particularly #46 all have monsters from the mythos in them, and we've done a few adventures in the Module line (notably Crucible of Chaos and Carrion Hill) that do more with these themes.
We'll be doing more. Because I loves me the mythos. And as it turns out, so do a lot of other folks!