I really hope they'll start to improve combats :
- no more backstab but flanking
- no more advantage/disadvantage for highground but a flat bonus
- disengaged untied to jump
- disengage as an action
- jump as movement
- no more food during combats
- 1 more party size slot
- proper reactions
Something else I'd really like is a D/N cycle.
I agree with everything above, but I'll expand a little.
- A revamped Reaction System
- Spells: Shield, Absorb Elements, Feather Fall (changed to it's proper Reaction type spell), Spiritual Weapon, Summon Beast
- Paladin class with Oath of Devotion and Oath of Vengeance subclasses at minimum; Oath of Ancients, Oath of Conquest, and Oath Breaker considered
- Smites properly executed
- Aasimar (pipe dream I know)