ugh seriously , I hate the old talent tree, first use your stone to teleport to a capital city, search for a class teacher, erase ALL your talent tree just for changing ONE single talent because it was more usefull for that specific boss.
With the current talent system you have more flexibility and the talents are more about your gamming preferences, with the former talent tree you were just a carbon copy of something that you researched in a forum.
And returning to the main topic, I will said that if Blizzard implement a 4th spec for the next expansion it was only going to be for the pure DPS classes.
Warlock = Tank (da with maybe a shield that consume your mana)
Rogue = Tank (dodge)
Mage = Healer with time magic
The only problem is the hunter, I dont see this class as a tank or healer
And adding a 4th spec that just do DPS for an already pure DPS class is a total waste of time, seriously