My guess is because she fled the eastern kingdoms to start her own nation, so the mages didn't included her in the council. She was still a member due to being a mage, but not on the ruling body.
But still, the OP (And people agreeing with him) are being incredibly deluded to think that the kirin tor and Dalaran would become alliance. Even worst saying on the title that its "Confirmed". I read the tweet of kosak, dalaran was not mentioned AT ALL on it. We've know 3 things from sound-files in the beta, and dev tweets:
A: Jaina will become the new leader of the Kirin Tor.
B: Despite being the leader of the kirin tor she will not be neutral, she remains alliance.
C: She may (or may not) become more aggressive, deciding to get rid of the peace she's strove to find and instead go to war.
How exactly does this means EVERY OTHER MAGE will follow her, I have no idea. As I've said before, the Kirin Tor has never been led by a single person. They're led by a council, and while said council has a chairman (It was Antonidas, then Rhonin) every desicion made by the council is still subject to vote. So no, no alliance-exclusive dalaran.
Jaina is the newest member of the council of six and that's all there is to it.
Por que odiar si amar es mas dulce? (*^_^*)
Late, but in regards to Alterac as per my idea: The idea behind making it an Alliance zone isn't to make it a low-level one. I'm talking level-cap, lore-heavy stuff that's there for players who want to get into the lore (much like the Lorewalkers), maybe with cosmetic reward items to encourage people to play through it. You start with Dalaran hovering over the Crater, and as you progress through the quests, Alterac gets built up into an extension of the city (which remains airborne and accessible by an NPC near the Crater offering to teleport you up to the room you teleport into in Northrend when you use the rune on the ground). A lot of the quests would deal with handling the Forsaken response to Dalaran returning and taking a pro-Alliance stance, as well as Sunreaver saboteurs and forcing the Syndicate and the ogre presence out of Alterac proper.
Actually, scrap the Alliance-only bit, make it a Contested zone with the ruins of Alterac built up into a Sunreaver base, with the theme based around the Kirin Tor (backed by Alliance troops) and the Sunreavers (backed by Forsaken troops) going at it, with daily quests for both factions and a quest line for the Horde establishing the Sunreaver presence there as a response to Dalaran's return and Alliance stance.
As the patches go on, daily quests could be added where you fight off an ever-increasing Forsaken siege on Kirin Tor-controlled lands, backed by Sunreavers who build the Ruins of Alterac up into a fortress of their own (Horde players would get dailies to bolster the Forsaken troops, attack prominent locations like choke points or ambush points, and escort Forsaken saboteurs into Dalaran itself, while Alliance players get dailies to kill the saboteurs, bolster the Alliance troops, attack those choke points and ambush sites, and sneak blood elf defectors into the Sunreaver base as moles or disguise themselves as blood elves to gather intel on the next step of their plans).
Come the Orgrimmar patch, things could hit full throttle and even when you're not doing dailies there, if you've completed the quest line for your faction you see the Alliance and Forsaken troops tearing each other a new one (collectively speaking), and Kirin Tor and Sunreaver mages lobbing spells at each other from behind the front lines.
Likely to happen? Probably not. Would it be actually kinda cool even if I don't like the faction war? .... Yeah, kinda.
Wow, this sounds very interesting but almost unfair for the Horde if they obtain an extra city that the Horde don't have
I'd also like to reiterate that datamined sound files do not equal confirmed lore changes.
So something happens to Rhonin.
Jaina doesn't go as apeshit as most people thought.
But what of the Sunreavers (or rather their pro-neutral leader)? If they really played such a vital role in bombing Theramore, thus leading to Jaine becoming leader of the Kirin Tor - leading to the Sunreavers getting kicked out of Dalaran and out of the Council of Six then that's pretty sweet irony really.
Amazing sig, done by mighty Lokann
"I quit WoW."
That would be a fantastic quest line. As Alliance you aid Jaina in kicking out the Horde and then teleporting Dalaran to some new location. As a Horde you have to hold off the attack long enough to get the last remaining Sunreavers out. After you complete these quests Dalaran in Northrend would be phased and not accessible to either faction. Then they could use the Sunreaver and Windrunner places in Crystal Song as a replacement FP.