Steven Wilson has already finished his nex studio album. And it will be totally different, when compaired to his most recent one, The Harmony Codex. He talked about it on the Gas Masks & Hand Grenades podcast:
The follow up is almost finished, can you believe. Bear in mind The Harmony Codex was finished in December 2022, so it's been over a year since that and I've almost finished the follow-up. It's very different again.

