This expansion has the potential for some of the best RP, ever. Bar none.
Yet it isn't happening, and the real reason I think it isn't? Attunements. (I HAVE LONG ASS THEORIES COMING)
When you had to do 5 heroics, three raids, grind five reputations to Revered or Exalted, finish up entire zones worth of quests that were long and boring and -really- required a group (unlike current and wrath quests), and -then- zone into a different heroic and reclear it to turn the damnable quest in, all to do tier -5- raiding (let alone tier 6), a lot of the people who -would- be PvE players and raiders said "Ah screw it all!" and RPed while waiting for groups.
Wrath saw the beginning of the end. Early on, you could find RP in Dalaran, mostly due to raiding burnout (in quest greens and blues, you could down Naxx. I know, I did it). Malygos on the other hand was too hard, badges were plentiful and quick and easy, and there was no dungeon finder, so your real options were "look for a five man group for another damn dungeon that you're already sick of" and thats about it. So there was RP.
Ulduar was similarly too hard- yeah it was easy towards the end of wrath, but even in ToC gear, a lot of people couldn't get past Mimiron, let alone hard modes. So there was RP.
Icecrown broke everything, because you had a raid with easy-ish intro bosses, a scaling buff that made you do better every week regardless of comp or gear, and three new dungeons.
Yes, there was RP towards the end when people got sick of Icecrown, but Cataclysm was pretty much designed to get rid of the timesinks inherent in the game. There's a series of dailies that you have to do... or you can run more dungeons, without even really looking for a group (yay dungeon finder). You have six or so reputations that you should grind, a bunch of achievement grindy things, but doing an almost unthinkable (since ToC) series of 12-18 dailies is now less than an hour of your time.
And they made alt levelling so stupid easy that a friend of mine managed to go from level 1 goblin, no heirlooms (but a 10% levelling boost from being in a guild), to level 85. In two months. Less, since it was mid-january I think he started. So yeah, there's no real limiters in place to keep you from the -game- itself, and so more people are enjoying that rather than RP.
Despite this, it will calm down and the game will become RP friendly again (moreso- look at the damn troll area in Org, its SO PRETTY AND I WANT TO RP THERE SO MUCH) but for now, there's just -too much to do-.
That said, I no longer need to do dailies, I've got raiding covered and I've done all the dungeons I care to (except a few lingering achievements here and there). So if you see me, toss a tell and if I'm not busy I'll gladly RP for a bit. Haven't really done it since wrath, y'know. Before then, honestly.