Something completely different is always possible. The new dialogue suggests that sylvanas won't show up in 8.3. That leaves basically every death related storyline unfinished which makes something related to the shadowlands the most likely. With the dragons on the screen again we could have a nice b plot of alextrasza vs bolvar.
We also don't know what happens after the n'zoth fight and we still don't know what will happen to the wound and the sword in silithus. Or the elementals, helya and all the races that collect azerite. Whats with his body? His visible part above sea level is about twice the size of nazjatar, the crucible of storms is a part of him. Do we just let him rot? No one seems to be concerned.
I personally wouldn't rule out a black empire expansion yet. N'zoth tested our strenght, instigated stuff for millenia, let us enter his domain and then just dies? And suddenly everyone is falling in love taking some time off, starts gardening, does their laundry? I don't buy that.