From what I understand of it, it is based off of EQ2 and the world for the second coming of Everquest. I think it is heavily changed as far as how the classes work compared to 1st edition, all for the better IMHO.
I might be wrong, and if I am somebody correct me but this is what I think they are doing with it...
Races are based on the new world...they don't limit classes to races like in 1e.
Classes are based on the new world, and there is a whole lot more of them now...they include a talents option for all the classes that is very similar to how d20 Modern does them. During character creation there are four archetypes to select from: Fighter, Mage, Priest, and Scout. Once you achieve 5th level, you may then choose to splinter off into a more advance class of sorts. These new classes will of course offer new class talents to select, and as you gain more levels (I think the next at 10th level or so) you can then select from the 24 real advanced classes:
assassin
berserker
brigand
bruiser
coercer
conjurer
defiler
dirge
fury
guardian
illusionist
inquisitor
monk
mystic
necromancer
paladin
ranger
shadowknight
swashbuckler
templar
troubadour
warden
warlock
and
wizard
and of course all these classes have their own disciplines and talents to choose from, adding together to the ones you have already selected. I think this will lead to a good assortment of ultimate customization not seen yet in a d20 fantasy game (of course, i could be wrong).
They are including a couple new races in the game, they eliminated attacks of opportunity, no half skills or cross-class skills to work with, all classes gain a defense bonus, armor provides damage reduction, and they are keeping the mana points for spells, recast times, bardic songs, weapon delay and most races (Vah Shir are gone).
I think they are also letting people select their starting feats based on race and class, providing more options.
Personally, this game sounds really amazing. The way they are doing classes, beginning with just four and THEN branching off into other classes is really cool.