DnD Next had an interesting blog post this week. It talked about the structure of classes and the way in which complexity will be organized. The main gist of it was that the game will use subclasses to introduce complexity. Fighters will have the Warrior subclass which is tactically simple and the Gladiator subclass that is tactically complex. For thug classes this seems reasonable since each main class can give a few abilities and leave a lot of the specific extras to subclasses. In theory this should be plenty to generate classes like Assassin, Duelist, Archer, etc.
For caster classes though everything is much more muddled, particularly since they apparently want to put classes such as Psions under the Mage umbrella. This seems problematic since caster classes seem to all have completely different mechanics and spell lists. Psions are thematically entirely different from Wizards and if they are to preserve the flavour from previous editions they can't reasonably be bolted onto the Mage baseline and will require a completely different set of powers and a unique spell list. Looking at the Mage I can see very little that can be ported over at all to a class that will use a Power Point pool instead of the utterly bizarre and terrible spell slot system that is currently in place.
In all previous editions spell lists ended up being a huge issue. Not only did every class get its own spell list but classes that were different thematically like Psions ended up having all of their own versions of spells with only minor variations on the originals published for Mage types. This lead to incredible bloat in terms of how many books were required and also made spell choice a serious issue. New players would be at a tremendous disadvantage to people who owned all the splatbooks that contained huge numbers of different spells, many of which were decidedly more powerful than the ones in the main book. Wizards seems bent on returning to enormous spell lists customized by class and to including old lore and themes at the expense of brevity and simplicity so Next seems headed towards the quagmire that was 3rd edition.
Honestly I don't see a good way around this problem for Wizards given their desire to retain the artifacts of the past. They obviously are dead set on enormous spell lists, clearly they will publish more spells in new books, and they want completely different mechanics (and thus spells) for many classes. There certainly are people who enjoy perusing thousands of spells to try to find the most appropriate *cough* overpowered *cough* spells but they have stated that they want to get the game back to its roots and acquire new blood. Those goals will not be served by encouraging people to spend endless hours perusing splatbooks. New blood is going to be attracted by making the game simple to learn and making character decisions straightforward not by encouraging system mastery.