Zovaal is a threat to everything, he wants to unmake all, not just life and death.
The great cycle is of course between life and death and unlike other opposing cosmic powers they have a connection like that.
Naturally, life seems like the logical next aspect to explore, maybe even in the same expansion but I don't think it will happen anymore.
We only got one patch left probably and they already have some much "story ground" to explore that including life just seems too much. And there I have not even included that the art team would need to do an entirely new kit of assets for the life realm...
So... if we get to the life realm it seems more likely that we do that in a new expansion and the best moment for that is after Shadowlands.
Personally, I don't want to go there, I would like that we stay on Azeroth and go there only in a patch if at all.