this has always been my guess as well.
i'm also guessing we'll see it on another card at some point (or maybe even a Ninja alt art, if for some reason they ever decide to make that one)
fun fact, Ninja is a direct copy of a breaker from the original Netrunner game, but that came out quite late in the game's cycle:
Femme Fatale is very similar to Black Widow, which is from the first expansion:
very few other killers made it from the base game. Codeslinger is likely the reference for Mimic (but imagine paying that install cost! Raptor could maybe ben the inspiration for Creeper, but that's probably a stretch.
i don't know if we'll get any more breakers from the original game, but i just really want a Big Frackin' Gun: