I think all but a few of the people in this thread are missing that the OP was asking to discuss actual problems in Pathfinder/3.5 that a new edition of D&D could address.
I definitely feel there are some verisimilitude problems with the number scaling, and even more with the economy.
Common guards, soldiers, and monstrous humanoids are weak compared to the creates that exists even at mid level, causing you to wonder how the intelligent races even survive. The flattening of the numbers will address much of this.
Magic item values are such that a powerful magic item is worth an Olympic pool filled with gold. And characters end up finding that much gold on an adventure. Which means that gold itself should be worthless as currency.
I'd like the source and workings of magic to be address in more detail, at least at the setting level. I don't need the rules to be complex, just to be grounded in something.
The three saving throws are an unnecessary level of mechanic, when the ability scores can do the same job. I'm glad that they're addressing that.
There are too many feats, which is where the system mastery problem comes in. I'd like to see feats reworked so that there are fewer of them, but each is more desirable.
A less granular skill system. Spending your points takes time, and each minor increase feels meaningless. While 4E took it too far, fewer, more meaningful ranks would be better.
Refinements to each class. Wizards could use access to some at-will magic in some form. Fighters could use some cool abilities. I think simpler forms of the druid and ranger would go over well with new female players, etc.
I wouldn't mind seeing classes restructured so there were fewer of them, but different talent trees or themes within them.
A greater focus on mundane equipment. I like cool things that aren't magical in nature.
A better system for spell resistance. I like the 4E concept of the spellcaster rolling, so SR could be a form of armor.
A well designed option for wounds and conditions for when I want more realistic combat.
A good set of rules for dramatic tasks, mass combat, followers, running businesses or cities, etc.
A wider variety in art, with a greater focus on setting and non-combat aspects of adventuring.
More love for the d12.
A rethinking of the place of wands and staves. Charged magic items make useful spells too powerful.
A revision of the way metamagic works. Instead of using a higher level slot, metamagic might required the use of an additional, lower level slot.
The ability to build NPCs and monsters on the fly.
A faster mechanic for iterative attacks and fighting with multiple weapons.
Generally more fluff in certain aspects of the rules. What, exactly, are undead and how does that work? Where do conjured effects come from? What do material components do for a spell? What, exactly, does a fighter's stance look like? etc.
