Nah. It's just a coincidence. I'm pretty sure that Oni didn't get the idea to put the X-Girls that he drew in 2015 into the game until 2017 at the earliest, which is when his pin-ups seemed to have stopped and the game was picking up steam. Also, one of his older posts mentioned that this whole game was meant to be just a one-off with Rogue only, and I remember another one saying that Kitty would have gotten her own separate game.
That said, that I'm basing this all off of what I'm seeing on Kemono. I haven't looked into where else he posts his art, like if he still does the pin-ups between game updates on Newgrounds, HentaiFoundry, or wherever.