No liches/sisters for the Infested. Yet anyway. They got Deimos and that wasn't as in depth as some might have wished.
That said? Infested are creepy and harder to make properly creepy from scratch as opposed to humans/armored clones are much easier to envision.
Personally? I would love more Infested lore and when we get Warframe 1999, we might get a glimpse behind the curtain of what happened leading up the the events of the original Dark Sector game. Probably not, but one can hope.