The biggest thing that is "Vancian" about D&D is spell slots. The concept of "knowing" a spell, using it, and not having it again until you "relearn" it is the basic essence of Vance that D&D took all those years ago. Everything else (spell levels, slots/day) are purely game mechanics to keep magic from dominating everything.
I think that is why when there are alternate magic systems, its not spell levels or such that go, its slots/day. Typically, its using some form of mana/spellpoint system.
However, the sorcerer himself shows that WotC is taking baby-steps away from the "fire and forget" paragrim. Proof? Think of every new core class that has come out since the first eleven in the PH (excluding alt systems like psionics or incarnum). How many of the ones that use magic use book/prep casting? How many use divine/prep casting? How many are spontaneous? Case closed.
FYI: 2 are book-casters (archivist and Wu Jen), 3 are divine/preps (OA shaman, Sohei, Healer), and 11 are spontaneous casters (beguiler, dread necro, warmage, mystic, shugenja, spirit shaman, favored soul, spellthief, hexblade, duskblade, artificer)