For me,
1) Cleaner monsters, with a focus on finding one cool theme per monster, and implementing it as well as possible with as few rules as possible.
2) Melee characters with flavor and variety to their attacks instead of just rolling to hit. I know you can always describe your attack with flavor, but when you attack 3 times per round and you fight two dozen rounds of combat per session, coming up with something cool each time is tough. Eventually you lapse into just rolling to hit.
3) Cleaning up the neglected parts of D&D that are technically in the rules but which most players ignore because they're annoying and don't do much. Like rules for switching between a cleric's shield, mace, and holy symbol.
4) Enlarging the sweet spot.
5) Making wizards and spellcasters more flavorful, instead of having your generic one size fits all wizard be the king of the casters.
6) Balancing magic so that a spellcaster can cast spells instead of fight in melee or sit around, while also preventing the nova/sleep effect.
7) Angering grognards.
And supporting points,
1) I don't know for sure how much of this will really happen. Some things, like making the sweet spot cover all 30 levels, there's no way to know until we get a chance to play. But the fact that the designers seem to recognize that there was a problem and to speak intelligently on why the problem existed makes me more confident that they can come up with a way to fix it.
2) Angering grognards isn't automatically a good thing, but sometimes they really annoy me. I like that D&D has changed with the times. Younger players have different fantasy heroes, and want to play characters that match them. This is a good thing, even if that hero was designed in Japan. The game should be as encompassing as possible. And honestly, if a player brings a character illustration of his barbarian to the game, and he's drawn a guy with big eyes, a small mouth, and a greatsword taller than he is, your game won't explode. Let him have his fun.
