It's true that we'd like to "narrow" wizards a bit, and save (for example) some illusion spells for an honest-to-gosh Illusionist class down the road, or necromancy spells for a Necromancer. But wizards will still "splash" at least a few of the iconic powers in these themes of magic. For example, wizards still have Invisibility available to them. But when the Illusionist class comes around, he'll have better Invisibility options.
After reading this, i think that if they are going to split wizards into illusionists, necromancers, and a wizards generalist, i doubt that we'll see monks, barbarians, druids and the other classes as talent trees of fighters and clerics... It's more probable that we'll see them as separate classes in PH2-3 ...
It just does make more sense: if you have to fill more PH with character classes, you can't just create a bunch of strange classes, but you must mix them with some appealing classes
I'm a kind of relieved of this discover, since this may be the only way to consider PH2 and the others, as truly core! I just hope i don't have to wait until PH2 to see the 4e bard!!!!