So last Friday and Saturday, Mike Mearls did an AMA on Reddit answering questions about DnD Next (mostly...). You can find the entire thing at the link above, but here were some takeaway quotes (good, bad, and ominous from my point of view) I plucked out from the whole:
So, the key lies in establishing the limits in each area and then, most importantly, throttling way back on the flood of mechanics. We have to consider each spell, theme, or whatever with the same attention that the Magic team regards a new card.
I'd like to incorporate a core "swarm" rule into the game, an easy way for DMs to group up monsters into single attacks.
...the aim is to make combat much faster (unless you want long combats - we'll have optional rules for that).
The simple rules we've shown off so far are about as complex as we want the core.
[Our] goal isn't to make everyone happy by making a game. It's to make a range of options that any individual DM can modify and reconfigure to make the specific type of D&D they always wanted and that no other edition was able to exactly deliver.
I think that 4e fans will see more stuff they like - the tactical rules module, maneuvers for fighters, other magic systems - as we move along.
Favorite campaign setting is Greyhawk.
We're using the 4e rules as a starting point [relating to adventure creation], XP budgets for adventures that scale with the number of players and character level, along with all-in-one stat blocks and a fairly simply math system for creating monsters/NPCs.
A little over a year ago, we went back and played ever major iteration of D&D from 1974 onward. That was our starting point for creating a list of features that the game needed to support.
The idea behind XP budgets and CR is to give DMs a tool to judge lethality. What they do with it is up to the DM to build deadly fights or whatever. It doesn't mean that DMs can't do what they want.
We want to go back to 3e multiclassing, but I think we learned some very valuable things from the hybrid system in 4e.
I'm a fan of the OGL. I think it did a lot more good than harm. I wouldn't have this job without it.
The XP system is the kind of thing where I want to do a few different systems and have the DM pick one (XP for treasure, XP for killing, XP for meeting story goals, etc) to establish the tone for his or her campaign.
One of the key hang ups we have with healing is trying to find a way to make the cleric optional. So, we're definitely aiming to make it so that you can remove classes, races, or entire types of magic without screwing up the game's balance.
The healing rules are going to get a complete overhaul.
[On the best aspect of each edition:]
0e - The core concept of an RPG, a game without limits or rails that is adjudicated by another person.
1e - Character options, creating a sense of the world of D&D rather than just a dungeon.
2e - Crazy cool settings like Planescape and Spelljammer, kits and stuff that tied characters to the setting.
3e - An easy core mechanic, clear rules for combat, a game that can be modified.
4e - Core math to build stuff, much easier DM tools, tactical challenges.