I will say what I have said before. WoW expansions are heavily teased not the expansion prior, but two expansions prior.
The Legion was heavily teased in MoP. Return of faction war stuff was heavily teased in WoD. Shadowlands was an important plotpoint at several points in Legion. And most recently we have BfA, that all but punched you in the face with all the dragon stuff.
Shadowlands is heavily teasing Light and Void, which is why I think it will be more important in 11.0.