I assume we might end up in the Astral Plane, especially because of Lae'zel's story and the whole Githyanki arc.
As for the effects it might have on us, Larian usually pays a lot of attention to detail and makes places feel unique. In DOS2 when the player ends up in Xantezza's realm of time, the player is drastically slowed down along with the music. Then when the player shifts the realm's time, they gain movement speed and the music tempo increases.
So I have no reason to think they won't do the same with the Astral Plane, as it's discussed quite a lot in the game, along with its effects. Even Lae'zel herself explains its effects and why Githyanki are born outside of it. So personally I'm quite hoping to see it in the full release, along with Vlaakith ^^
