Honestly I think they’re moving away from the sex stuff with Slaanesh’s characterization, and I kinda like one possibility for where that could take them

The eye of terror opens with Slaanesh’s birth, and only doesn’t explode into the great rift because of the Blackstone on Cadia holding it as closed as it can without being repaired.

Event Horizon is often jokingly theorized to be about humanity’s first contact event with the warp, and people will sometimes treat chaos portals as functioning similarly to black holes.

There’s a little known fact out there that you can create a black hole by making a loud enough sound, and Slaanesh’s big thing aside from sex and drugs is copious amounts of sound, their special chosen marines are even called noise marines.

So what I like to imagine, is that the Great Rift is in fact a Kugelschreik (where a Kugelblitz is a black hole made by forcing enough light into one place), a galaxy spanning black hole ripped open by Slaanesh’s screams of tearing themself into existence in the warp on the back of overwhelming Eldar agony in the name of excess and sensation.