As far as eclipse goes: [Hurricane] will have an arcane version for players that find themselves on the other side of the bar
Druids will lose their ability to pump out DPS, then pop into bear form and tank; this change is intended to bring druids more in line with other tank classes, as their is now the Feral (cat) and Guardian (bear) specs.
For characters that use transfer services, often the quests they have are wiped. This includes legendary quest lines. It "would be nice" to have a "white-list" of quests that are excluded from this. Good idea, but not in development right now.
With companion pets having a shared page across all characters, the same might be done down the line for things like mounts and heirlooms, to avoid the need of sending them in the mail
Guild services, such as the promised name change feature, will be delivered in two weeks.
Options right now that are only designated for Guild masters may be able to be delegated sometime in the future, but the concern is players abusing those powers and hurting the guild, which Blizzard would then have to deal with.
Just as they're planning on provided cosmetic upgrades to Hunters with the showing of quivers and ammo pouches, they're looking at doing this for all classes in some form or another. An example was for paladins: even though relics are being removed, they want to still provide the visual component of librams.
Blizzard understand how hard it was to obtain certain items (example was [Benediction]) when they were relevant. Want to reward players who worked hard for the items, so thinking about introducing the same models, but with different textures to differentiate between the "newer" version and the old version.
Illidan Stormrage seemed to be a popular character that Blizz was willing to look into bringing back, but not necessarily for this expansion; when it fits.
Arthas Menethil: no word on where his body is after he was killed. No confirmation whether the tomb in the Stormwind City Cemetery is his or not. Others of Arthas's family whose whereabouts/disposition are unknown: Arthas's sister and mother. Chris Metzen likes the idea of his mother having died before his corruption at some point, but nothing is for certain.
Tyrande Whisperwind and Jaina Proudmoore are going to have their days, soon. Just as Horde characters have recently had their stories fleshed out, Tyrande and Jaina are on the block.
Varian Wrynn: to that end, Varian is also going to have his story fleshed out, so that there's little question as to why the Alliance races should follow him. Metzen envisions something along the lines of the labors of Labours of Hercules, where Varian has to complete monumental tasks for each of the Alliance races to prove himself. Players might get the chance to come along as something like his squire ("Trials of the High King"). It seems there's a desire to put Varian at least somewhere near the same level as Thrall.
Is Baine Bloodhoof a Sunwalker? Unlikely, as the vision of Baine is that he's an earthy Tauren, just like his father, and magical abilities and such would get in the way of that.
It seems that Bolvar Fordragon might be doing nothing in Northrend with the Scourge, but we're assured that isn't the case. Of course it seems that way in the game, as players need to progress through and complete those quests. Metzen, if he were novelizing it, suggested that the Scourge would actually become dormant in Northrend after Bolvar's ascension; however, he also said that the Scourge in the Plaguelands should be considered autonomous to some extent, maybe driven by something other than the Lich King at this point.
Sylvanas Windrunner has a limited amount of Val'kyr-based resurrections left at her disposal. Four, it seems, if the numbers are correct. This is because there aren't many of the Val'kyr that remain, and she cannot make any more of them. On another note, it was said that the number of Val'kyr required for a resurrection is based on the age of the participating Val'kyr: the older they are, the less of them that are needed to sacrifice themselves.
The pandaren in the beginning zone, the Wandering Isle, are considered to be a little different culturally than their brethren away in Pandaria due to the thousands of years that have passed since their split. This is why these particular pandaren can choose between the factions, whereas those on the Pandaren continent wouldn't be as likely.
Even so, there's no true hatred or animosity between pandaren after they choose their faction.
There's no true ruler of Pandaria, despite having an emperor in the past. The leadership is more described as venerated figures, of which Chen Stormstout may be a part of.
The Zandalar make a return in the expansion and play a role in Pandaria. Their mission is still the same: the reunification of the troll empires, and it seems they're "driven by something"