No, there's been no announcement of a novel, and at this point I don't think such a thing would be likely. What you probably heard second- or third-hand is a version of what Miura said in his video, which is being exclusively shown at
the exhibition.
Here are two interpretations of portions from that video:
Source:
https://twitter.com/behegotchi/status/1436775838301634564?s=20
Source:
https://twitter.com/sandman_AP/status/1437031645903687680?s=20
Given that the video is exclusively for exhibition attendees for now, we can't verify anything about its contents. So we have to rely on these little text blurbs. But one big thing neither explanation took into consideration was the timing of the video's recording. Miura wasn't referring to something NEW about Skull Knight, but something old. That video was recorded sometime between Nov-Dec 2020, a bit before the exhibition was originally slated to debut in January 2021. And consider, in that time frame Episode 362 was the current release, which included a story about Skull Knight's past. That accounts for this part: "Young Animal is currently running a series about skull knight's past." From Miura's perspective, 362 was that.