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.
Background Skills
Add more examples to how to apply background skills
Codify manufacturing skills and times for mundane items
Rebalance manufacture times for armour in general.
Codify costs and times around Masterwork Equipment.
Rework Trollskin, add a Heavy Armour equivalent.
Clarify effects of missing various limbs
Improve Illuminati (add free Guild mana usable in sunlight, increase sun healing rates)
Regrow
Rework regrow missing limb option.
Reattach
Balance against regrow. Somehow. Add to rules as freely accessible casting.
Healers
Revisit Guild Restrictions
Disable Trap
Add an AOE trap removal effect to stop double trapping working
Wardens
Rework
Stunned
Give a free defenceless hit before targets affected can defend themselves
Demon Hunters
Make totally immune to Wrack
Castings
Add a Divine Attunement Miracle. Reduce Discern Path 1 level and add as pre-requisite
Other Temples
Add refund to temporary temple of chaos bonus.
Add armour masteries
Monster Manual
Rework Monster Manual. Add broad categories with descriptions and consistent immunities/vulnerabilities.
Update the monster skill tables. (They’re probably out of date somewhere, like all the shield costs)
Move Armour Standards into the core rules.
Amazons
Get a new Guild Logo