Someone on another board suggested something that I thought was mechanically quite brilliant for a new edition - unify the classes by power source.
So each class got a pool of abilities to draw from based on their power source (Martial, Primal, Divine, Arcane) and then class specific abilities to add on to that.
That would reduce a lot of the 'overhead' in D&D, as a common pool of powers makes a lot of sense, and generally unifies game balance. Why SHOULDN'T the Avenger, the Cleric, and the Paladin all have a set of unified powers they can draw from? They're all warriors of their gods who hit things with weapons. It makes introducing new classes a lot easier. Why shouldn't the Wizard, the Warlock, the Sorcerer, and the Swordmage all pull from common spells?
4th edition succeeded in being the most tactically interesting, balanced, and fun to manage edition of D&D ever. Gone were the days of banning 4 core classes for balance (bye Wizards, Clerics, Druids, and Sorcerers). Gone were the days of flinching when 4 people decided to roll up a Monk, a Wizard, a Cleric and a Rogue to drop into a 9th level campaign.
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As for new directions, 4e has taught them a LOT. MM1 and MM2 were a little shaky, but with MM3 and Monster Vault monsters, I can consistently throw at the party, as a DM, challenges that leave them on the edge of their seats struggling to find a way to handle everything that's coming their way.
This is a feeling 3e has never really succeeded in creating.
I think that there's a lot coming for a new edition - truly unified tactical combat, a nice mix of simplicity and power, and a strong ability to create interesting systems on the fly.
P.S. The internet tends to massively overestimate Pathfinder's fanbase. It's a very solid system, and went a long way towards adding some fun back in 3.X that eventually went missing, but it is an okay patch on a framework that DOESN'T WORK.