These are the things the Character Ref team are currently thinking about changing/adding to the rules. None are yet set in stone and more details will come out closer to the time.
Look at shield costs at higher levels
New amazon draft
Revisit traps, looking at moving Trigger Trap and Hold trap to scout abilities, and some instant traps to make more usable as a player.
Reword wording around Path of Nature to remove unintended miracle stacking
Healers
Add to game
Regrow
Rework regrow missing limb option.
Reattach
Balance against regrow. Somehow. Add to rules as freely accessible casting.
Background Skills
Add more examples to how to apply background skills
Codify manufacturing skills and times for mundane items
Codify costs and times around Masterwork Equipment.
Armour abilities
Add in some form.
Items
Add Rapid Attunement as an item option
Add examples for resolving Bound and Attaching items.
Monster Manual
Rework Monster Manual
Revise/Define phys-rep standards for armour.