With all the new 4e new designs so far I like the wizard ideas I really hope that they are expanded. The other focus I hope to hear about is the psion or psionic characters. Dungeons and Dragons in my opinion just keeps getting better.
Magic saturates the world and all the extraordinary realms beyond the world, an intrinsic force present in literally all things. Magic transforms and alters the natural world, sometimes actively and with sudden effect, other times subtly and over long centuries.
This arcane energy source is difficult to understand and even tougher to master. Wizards do so through years of study, practice, and apprenticeship to accomplished masters.