What I expect?
Essentially cosmetic changes mostly, and a different presentation of the same things we have now.
I expect changes to core ranger and beast master subclass, in line with Tasha’s optional variant ranger features.
I expect removal of fixed ASI at character creation, but little changes to other abilities.
I expect (and hope for) a rationalisation of « pet » rules to a universal « acts on your initiative but takes turn after yours » for companions, mounts, familiar, and conjured creatures.
I expect minor tweaks to some subclasses like champion (despite being popular) and 4-elements monk.
I expect some rationalisation on reactions, bonus actions, and their timing.
I expect a few more subclasses offered as « core » in the PHB, especially to classes with two presented archetypes (but not an anthology of all splat published so far).
I expect (and hope for) a little more diversity in monsters’ roles and abilities, and 1/day spells and spell-like abilities instead of player-like spellcasting.
I’m not sure if I expect the artificer to make it into PHB. Somehow I don’t think it will.
What I want?
I want an in depth review or what spells require concentration and doesn’t, and whether they should or shouldn’t.
I want more monster spellcasters. If you’re to publish mostly spellcasting PCs, grant us more ready-made spellcasting antagonists. Or a selection of templates as add-ons.
I want no-magic and low-magic how-to-guides in the DMG.
I want minor but thematic rule variants for specific settings (unlikely to happen given WotC's multiverse approach).