Oda is building up Kid to be one of the great pirates of the worst generation. As his vice captain, killer should have it imo.
So far, almost every great pirate has shown to have a CoC user serving under them. Roger had Rayleigh, Oden, and Shanks; Whitebeard had Oden and later Ace; Big Mom has katakuri; Luffy has zoro; and Xebec had Big Mom, Kaido, Whitebeard, and possibly Shiki.
Overall, given that Kid is built up to be one of the top 3 captains of his generation, I think it only makes sense that his vice captain, Killer, will also have it. Especially since Killer is a rival of zoro. Yes, I know Zoro is much stronger, but Killer is still a rival in spirit as he's the right hand of Kid(which at the very least, is more of a justification for him to have it than Sanji).
The way I look at it; Luffy= Roger, Kid= Whitebeard, Blackbeard= Xebec. Both Roger and Whitebeard had CoC wielding first mates(oden not marco).
Anyways, I don't think he will get it this arc, albeit Oda could always surprise me. But I wouldn't be surprised if towards the EoS, Luffy runs into the Kid pirates and we see Killer have a CoC clash with Zoro. While Killer might not be the most flashy of the supernova, his portrayal as one of the 5 supernova on the rooftop is a clear indication that there's something special about killer, even amongst the supernova.