Probably. It just depends on new sources being found as well as artwork and stats for them being created. Adding creatures is pretty low-effort and low-consequence, so there probably wouldn't be as much of an issue with adding them as there is for, say, new ships.
Creature art, for the most part, was ripped from other sources long before the current art team standards. Currently new creatures would require new custom images, but I only know a handful of people capable fo doing that.
Zhao had previously changed the requirements on biological entities to allow them to be 2D or 3D, unlike ships/droids/etc which we require 3D models. The rationale being that artists capable of doing creatures/races in 3D were incredible hard to come by, and the products often didnt look as well as 2D painted ones.
Dunno if thats still the standard.
We've randomly added creatures over the years, a number were added back when we revamped them a few years back.