Will it be added?
Hard to tell. Very unlikely at short-term... maybe in long term. The problem here is that, while we have various people capable of making maps, we have very few people who put their hands on gamecode to fix bugs and to add new features, and only one artist who makes 3D models. Development of OA is very slow....
By the way, if you want to fight monsters, you may try "Save the Universe" and "Escape from Hell" modes of "
Hunt" Q3 mod.
(
DO NOT LINK) h t t p s : / / openarena . wikia . com/wiki/ModCompat/Hunt
Note: you really should read the compatibilty infos in that wiki page to be able to play it under OA.