Doug McCrae said:
For 3e fans I don't see any drawback. All your 3e books will still exist and what's more you'll be able to buy the ones you don't own cheap. Wizards were going to run out of things to make into feats and PrCs pretty soon anyway. 4e will be an additional option. Something to try or mine for ideas. What's the downside?
The downside is that going much further will take away pretty much everything that makes D&D, D&D. There are certain things that simply
are D&D - classes, levels, hit points, etc. Take those away, and it's not D&D anymore, and probably encroaches upon another game that already exists and does it better. I didn't see much call for, say, GURPS, RuneQuest or Warhammer to be totally different systems with their current revamps. I don't see why D&D would have to be totally redone, either. Those who want to play a totally different game should play a totally different game. There really are a lot of them out there, and many of them are very good. Plus I dispute that people wouldn't buy a "3.75e," especially if it cleaned up the problems that have been unearthed and presents the game in an attractive, accessible format.
What I'd like to see in a 4th edition of D&D:
A truly basic version of the game. Include it at the beginning of the core rulebook, and layer complexity on top of it in succeeding chapters. That way players can choose their level of complexity with an option to go up or down on the scale. Release the basic version as a complete, standalone, inexpensive game to satisfy those who are looking for a quick, beer & pretzels RPG.
More optional rules, such as those found in Unearthed Arcana (action points, defense, etc.), placed in the core rulebooks.
The Warlock - it covers an archetype in comics and movies that really hasn't been covered well in D&D before.
That's all I can think of at the moment.