Alas I think we should not expect any "very comprehensive" thing for AoS
GW & Cubicle 7 will keep things open, and I guess it's ok, if the fluff keep getting fleshed out as it is since Season Of War "Seeds Of Hope" and "Firestorm" (and the novels like City Of Secret, Spear Of Shadow, Hammerhal, etc.)
A well developed setting would be nice, like a Great City dedicated to the RPG (or why not Hammerhal) - they did that in 4'k with the Dark Heresy Calixis sector.
The timeline I'm not sure it's likely either - but they should introduce at least centuries in their timeline. Or expand the "Annals Celestis" thing they have for the Azyrites.
I disagree on only one point : new deities wouldn't fit the established narrative of "gods or Incarnates form the World-that-was = pantheon of the Mortal realms".
What could be done is to add more Godbeasts, or "Elemental" entities, like the Ur-Phoenix, which has aelven worshippers, or the Fulminax.
We can all agree on one thing : it will bring more fluff and details to the AoS universe, and this is great !