I’ll start by stating: I like Vancian Magic. While I didn’t play many straight Magic-Users under 1st Edition Dungeons and Dragons, I frequently played the illusionist sub-class and enjoyed the heck out of it. Part of the fun of playing with a more limited set of powers is trying to find the right moment to apply those powers.
With the new editions stated goal of allowing different types of play within a single framework, I think a place should be made for Vancian Magic. This doesn’t mean all magic use should use the fire and forget method, but I do hope that either upon release, or in a module released very shortly thereafter the new edition includes one or more classes built around the idea of Vancian spellcasting.
I like the idea of including the Vancian spellcaster right from the start. In my mind this would probably mean including at least 3 arcane spell casters starting with the core rulebooks. Bring back the class of Magic-user from 1st Edition to represent the Vancian casters. Add the Wizard to represent casters tied to studying and memorization but built along a more modern version of the rules set. And then the Sorcerer to represent casters who harnesses some inner force to cast their spells. Potentially the Sorcerer and Wizard can be built from the same class and differentiated by feat or power choices.
I do think some allowances should be made within the Vancian caster to make them a viable option though.
They will need access to more spells at low levels than the traditional Magic-Users had. This could be by simply giving them more spells, or daily powers per day, or by including feats or class abilities that allow for recovery of cast spells. Using 4E terminology, I would allow Magic-Users a fair number of daily powers, while eliminating all their encounter powers.
They also need some access to some useful at will abilities. For a high-magic campaign, something like a magic missile that requires a to hit roll, or a magic pebble spell which always hits but only deals 1 or 2 points of damage. In a low magic game, the ability to do something like daze an opponent for one round with a successful attack using a specific ranged weapon could keep the Magic-User out of melee while still allowing him to take a more active role in combat.
While I’d like to see them at release, I think it is more likely the core release will have casters built in a method closer to the 4E rules. Because of their goal of allowing varied play styles I think the Vancian caster will release fairly quickly after the core rules, either in an online article, or in a splatbook covering one or more alternate magic systems.