In my view, World of Warcraft has become more accessible than it has been since its dawn in 2004. In Burning Crusade, we were given Daily Quests for more stuff to do a day, Heroics to do more challenging dungeons, flying mounts and Badges of Justice.
Wrath of the Lich King brought us the Emblems of Heroism/Valor/Conquest/Triumph/Frost, Dual Talents, PvP Zone with optional raid, zone phasing for story purposes, the ability to change your hair in-game and Dungeon Finder.
Cataclysm turned those badges and emblems into Justice Points, made certain classes more available for various races(Ex: Hunters for Humans, Mages for Orcs), Reforging, simplified stats, Transmog for cosmetic looks and Raid Finder for beginner raiders.
Mists of Pandaria has brought to us Scenarios(Which turned out to be more popular than Heroics), Pet Battles for those Pokemon fans, Challenge Modes for those wanting to beat their time in Heroic Dungeons, Companions and Mounts now account bound(With some exceptions) and the return of World Bosses.
And there are some features I may have missed out on talking about.
Beyond that, what would you guys like to see in a future WoW Patch/Expansion?
I would like to see Transmog gear give the ability to change color, the ability to replay classic dungeons/raids the old fashion way by ether scaling the player down to that level or the dungeon/raid up to the player's level, and more Solo Scenarios.