I hope Blizzard will keep an option to play shadow priest as a pure shadow in future instead of void. Like Forsword in SL. I disslike void fantasy, i like dark magic theme: ravens, wings and etc, like it used to be in all old expansions.
Maybe make two sub talent trees in future expansions, but let them be more distinct from eachother: Archon - ravens, wings and shadow magic. Like Forsworn in SL. Void - tentacles, old gods and madness.
Archon should be a separate talent tree. With wings like Forsworn (those dark valkiries) in Shadowlands. Look at Lysonia NPC at 1:05 she even has the mind fly ability (but grayish).