Before you go much farther, I'd recommend reading the full transcript of mage-specific questions and answers. It's some pretty good stuff. For the purposes of brevity, I will be condensing each of the answers given into shorter, more tightly wrapped nuggets of information, then discussing each of those nuggets with slightly less brevity.
DPS vs. utility
After patch 5.0, frost will no longer have to sacrifice DPS for utility. One of the most intriguing aspects of the talent revamp Blizzard has planned for Mists of Pandaria is that by making every major spec ability baseline and making most of the talent choices utility-based, it's hopefully laid the groundwork for true equality between the DPS specs. With proper balancing, there's no reason any of the three mage specs should be able to eclipse the other two in terms of PVE potential. As the developers state, the only difference should be in which spell you're using to do the damage.
This is an oversimplification, but what I'm picturing is something like this:
Fire's main nuke will be Fireball. Frost's will be Frostbolt, and Arcane's will be Arcane Blast. None of the other specs will have access to any of those spells. There will be other parts of the rotation for each spec, to be sure, but under this new model, all of those spells will be spec-specific abilities that the other specs don't get to use. Spec specializations that increase school damage, like Fire Specialization, will no longer exist. This should make balancing very simple. Each spec's main rotations will be balanced so that in equal gear, mages of equal skill level will be doing equal damage under equal conditions.
Any outliers, like Scorch, which is currently spec-specific but will become a talent available to all classes at level 45 in 5.0, will be equally viable for all specs. With no Fire Specialization making it more attractive to fire mages than arcane or frost mages, anyone who selects it will benefit as much from it as anybody else. And since the other two talents in that tier are also movement-based DPS spells, Blizzard should be able to balance those talents against each other, so that there is no discernible DPS advantage to be gained by selecting one or the other.
Basically, if implemented perfectly, this new model should allow all of our choices (all six of them) to be entirely based upon playstyle preference, as opposed to gaining a damage-potential edge. That means that no longer will frost be the PVP and utility spec, and no longer will fire be the AOE spec, or arcane the spec you have to take because your raid leader insists upon it. Frost will simply be the spec you take because you like frost spells. Or because you think the rotation is more fun to use. Or because you like your warlock bits served cold.
Will things actually work out this way? I think there's a fair chance that they will. It's a solid groundwork Blizzard's got laid here. It's radically different from what we're used to and will definitely have its detractors, but going forward, I think it provides a healthy base to build from. It should be relatively simple to balance and allow more freedom in spec-selection than we've ever had before.
Arcane's rotation will be getting more interesting in 5.0. Though the developers stated that they want to keep the mana management aspect of the spec mostly intact, they do plan to add more spells to the arcane rotation. Most notably, they plan to make Arcane Barrage a necessary part of the repertoire. I'm pretty sure I have asked for that in this very column approximately 832 times; I didn't go back and count, but that number seems accurate. Arcane Barrage is a very cool spell. It's instant, on a short cooldown, allows for added mobility, and looks sweet-ass. It needs to be a big part of the rotation.
The developers also mentioned that they've been toying with the idea of a moving Arcane Missiles but haven't yet figured out how to make it work. This is another concept I'm fully in favor of. Barring the addition of any new arcane spells, the arcane spec has three spells that should be a big part of the regular rotation: Arcane Blast, Arcane Barrage, and Arcane Missiles. Those are the spec's signature spells. And right now, Arcane Missiles is just a spell you use during your conservation phase to dump Arcane Blast stacks. It needs to be something more than that, and allowing it to be cast on the move would be just about the perfect solution.
A few additional spells
The MoP mage talent tree could use some additional spells. The specific issue asked about was the three spells offered at level 90, which are all spells we get now at much lower levels. Blast Wave, Dragon's Breath, and Slow are all good spells, but as the cap talent? It seemed as if every other class was getting access to something entirely new at level 90, but mages were getting old news.
The developers agreed that the tree could use an infusion of new spells. I'm not worried. This expansion is still a long way off, and the trees we saw at Blizzcon were still in their infancy. Let's see how things look in six months.
Cold, hard choices
Having to choose between Cone of Cold and Ring of Frost is apparently a good thing. The claim is that frost currently has too many CC options, and by removing two core frost CC abilities from the spec and forcing us to choose between them as talents, we free up design space for Blizzard to add new and interesting CC abilities later on.
This goes along with the concept of spec equality that the new talent design seems to be striving for. By equalizing the CC abilities between the specs, the developers effectively remove the whole concept that spec A is the utility spec, or spec B is the PVP spec, or spec C has to sacrifice DPS for control. They take frost's CC options, put them on the same level as arcane and fire (and comparable, I would assume, to the other classes), and spread out the extras as talent choices. The frost mage who now has to choose between Cone of Cold and Ring of Frost feels like he's lost something, but the frost mage who suddenly finds that he's doing the same amount of DPS as the arcane mage feels like he's gained something.
Equality, people. That's what they're trying to do here. For better and for worse, everything will be completely different when the expansion hits. If designed properly, the specs will still feel unique but will do roughly equal damage. By removing some of our choices, the design team will in reality have give us a freedom that we've never really had before: the freedom to choose which spec we want to play based on which spec we want to play.
Everything else aside, you have to admit that would be nice.
Every week, Arcane Brilliance teleports you inside the wonderful world of mages and then hurls a Fireball in your face. Start out with our recent beginner's guide to being a mage, then check out our three-part State of the Mage columns on arcane, fire and frost. Don't forget to look at some of the addons your mage should probably be using.