Rather than clog up the existing 3.2 threads here is the 4.0 information.

General Information:
You get 5 talent points at level 85, but the trees are staying the mostly same (some talents could change or shift positions). What is being added is talent mastery (which gives bonuses if you put more talent points in one tree than another).
The plan is to get rid of improved Blessing buffs and maybe spread around availability of Paladin Blessings.
Reforging affords tailors, blacksmiths, leatherworkers, engineers, and jewelcrafters the opportunity to customize any player's gear, including their own. Specifically, they can reduce a single statistic on applicable items and convert the lost points into another stat not already on the item (less worrying about exp/hit caps).
Every healer class can dispel magic.


Retribution:
No more agility/AP gear: replaced with agility/strength only gear, so every dps gets 4 stats on gear (more stamina for everyone!), so Ret wants Plate gear.
Armor Penetration is removed. It is being replaced with Mastery, a stat that makes you better at what you do.
Haste: Will also increase the rate at which you gain energy, runes, and focus. Retribution paladins and Enhancement shaman will have a talent that allows them to take advantage of this benefit, since Ret/Enhance will be the only physical damage classes with mana.
Shadowmourne is the Icecrown 2H Axe legendary. Only available to death knights and hunters?


Holy:
Spell Power and Mana per 5 Seconds stats are removed.
All healers use Int and Spirit.


Protection:
There is no more defense rating. Each tank gets a talent that reduces crit, so no need to worry about the "defense cap".
Block Value goes away, block (just one unified stat) is now a reduction percentage of incoming damage.

Ret and Prot certainly are resource limited (the small mana bar). You are right that doesn't apply to Holy though.

Not really, at least not in the sense that the other melee classes are.

Think of it this way. A Rogue's outgoing damage is tied directly to his Energy bar. He can only Sinister Strike when he has a certain amount of Energy, and after then he must wait a period of time for his resource to replenish enough to use a second Sinister Strike. Thus he is throttled by resources. The same is true of Death Knights, Warriors, and Kitty Druids. This change is a net buff because it lowers the recharge time between attacks, allowing him to attack more frequently and deal more damage.

If you're playing Ret or Prot correctly (and with decent raid support for Ret, at least in the current iteration and hopefully something they are looking at actively for Cataclysm) you are not throttled by your mana bar. The mana you are getting in through DP/SA/BoSan/JotW/etc. balances out the mana it is costing you to maintain your rotation. Thus we are throttled by cooldowns: we have to wait for our ability to come off cooldown before using it again. This haste change would not buff us, our resource supply is (ideally) already high enough that an increase in it affects nothing.

They could make something like Consecration cost a lot more mana, so with more Haste you gain more Consecration casts, but that is a fairly clunky fix. They could make haste lower our limiting factor (cooldowns), but that has the potential for some serious PvP ramifications.

In short, there isn't really an easy solution I can think of, but I'm looking forward to seeing how they tackle it.

Not really in the same sense that rogues/hunters are (well, hunters with the cataclysm changes to get rid of mana for focus).

A rogue's combat cycle is almost entirely resource-limited - nothing they use has a cooldown, they're just constrained in how often they hit buttons by resource requirements, since they can empty their energy bar in a couple of GCDs but it takes 10s to fill back up (well, slightly less with energy regen talents, etc). Increased regen provides a direct DPS increase as they can hit buttons faster. The same goes for DKs with rune recharges, and by the sounds of things, hunters will be the same with the new Focus system.

Ret on the other hand is only resource-limited in the long run - until you have to hit Plea to keep going, you're just hitting every button as soon as it comes off cooldown, so increased regen does nothing for your dps, except maybe a single GCD every minute or so saved from not hitting Plea.

Unless of course they plan to move Ret to a more rogue-like system (much higher mana costs, but JotW providing a buff that fills your mana bar over 10s or so, boosted by haste, along with getting rid of the cooldown on CS, or something along those lines, maybe?)

Again though, this would lead to weird disconnects in gearing based on raid buffs. For example, Haste would become an incredible small group/solo stat but would end up being quite poor in a full raid where you do get those regen buffs that easily make up the regen that you need, making the extra regen from haste worthless. I think its a lot more likely that we'll see Ret regen/consumption as a whole addressed and see Haste have some sort of other benefit.

I'm gonna assume they wouldn't make a legendary for only DKs and Hunters, as Valynyr was for 4 classes. Warriors and Paladins probably get Ashbringer, or Ashmourne, or something. I assume they wanted to add 2-handed legendary, but thought it would be dumb to have Hunters and DKs using Ashbringer.

They absolutely can't have ret-haste work as a regen mechanic, otherwise you'll simply see Son-of-TbtL builds as healing pallies wear holy gear with ret talents for the massive regen.

Why can't it just be as simple as "This talent increases your AP by your (haste/2)%."? (Plug in a better value for 2 once determined.)

Eh, they've made Legendaries for only one or two classes before (Warglaives and Thoridal specifically) so it wouldn't be something new. The blue post recaps of the panel on both the US and European forums specifically state, though, that it is intended to be for Death Knights and Hunters alone. How that will work specifically is left up in the air given the massive stat disparities between the two classes.

Regardless, it isn't a hugely important issue at the moment.

This is my guess for what they will do - create a talent that allows haste to reduce all DPS cooldowns across the board. It won't necessarily have much impact on PVP if there is no gear with both haste and resilience on it (which presumably would always be the case for PVP gear), especially if they can succeed at making resilience as necessary a stat for melee DPS as it is for healers and caster DPS.

While I can understand that the upcoming expansion is very exciting, it's also long enough away that I'm going to have to ask you to keep your discussion about it in the BlizzCon thread. We'll be fine with class specific discussion once it's beta starts and NDA has been lifted.