F-Axis enemy within had what - about 12 species not counting variations (Heavy/Commander etc.) and has recycled most of Xcom Enemy Unknown creatures?
Easiest way would be to recycle all creatures from Laser Squad, Xcom, TFD and Apocalypse.
I believe it will not be much recycling due to copyright reasons and a wish to distigish it as new game, no matter how much I would love to meet Sectoid or Lobsterman in this new and advanced game.
They seem to drawn inspiration from more Lovecraftian and ancient mythology/horror parts then Sci-Fi like it was for LS/XCom Enemy Unknown.
I find story of virus and mutations nice and “Resident Evil” like, but would not speak of mutated elephants until I meet one.
DLC should bring more, first is announced free, underwater missions one (that might bring TFD like creatures) will be paid one. And as usual, that is all next year to release.