You can also chatch a live stream (text) of what is being said here:
D&D XP Seminar: Class Design - Live Blog Live Blogging
Bruce: We definitely want the classes to be balanced, though having things exactly mathematically balanced isn't always the goal. Different classes or different play styles will shine at different moments, though of course we want everyone to be able to contribute in the common situations like combat.
Bruce: If the fighter is 100% damage for example, then maybe this other class is 80% damage/combat and 20% exploration, or some other mix of game elements.
Monte: I know it's a bit contreversial, but I think Vancian magic is a core element of D&D. Maybe it's not the only option for magic, but it's definitely an iconic and flavorful one that I would like to retain. It's also an interesting way to handle game balance. For example wizards have magical feats that are basically at will abilities. Balancing them with vancian magic which are essentially daily abilities is an interesting way to go, especially when comparing to the fighter and rogue who have more of an at-will style play. It offers a very different playstyle than those other classes, but those different playstyles are something we want to embrace.
Greg: Those at-will type of attacks are things that have come to D&D with 4th. How are you guys integrating that in the next iteration.
Bruce: As monte mentioned, you have those feats that give you at-will style attacks, and some spell or class options will give you at will kind of attacks.
The fans have got to do the rest, so if you want to see a successful D&D game going forward we will all have to look real hard at ourselves and decide to be inclusive and not exclusive.
I already have a successful D&D game going forward, it's called Pathfinder. I'll only change that if I see an opportunity for a better D&D. Sorry if that makes you upset, but my concept of a "better D&D" has a lot to do with what stays in the implied setting, and if I'm ever going to DM this edition, I want dragonborns to stay confined to books like 3E Races of the Dragon. The same goes for shifters, warforgeds, genasi and other equally "creative" options.
Cheers,