PC gamers had to live with years of news predicting the "death" of the PC game, based on decreasing retail sales of PC games, and increasing sales of console games. Until NPD started tracking MMO subscriptions as well, and suddenly the PC games market didn't look all that bad. It doesn't take a genius to figure out that if MMOs are one of the most lucrative segments of the PC games market, and there are more console gamers than PC gamers, there could be a fortune to be made with console MMORPGs. Or couldn't it?
The first problem on the way to console MMORPGs is connectivity. PCs were simply connected to the internet earlier than consoles were. But the current generation of XBox 360 and Playstation 3 is fully internet compatible, and there are millions of gamers on services like XBox Live. So while earlier games like Everquest Online Adventures or the console version of Final Fantasy XI might have had problems finding enough customers with a broadband connection, that would probably not be a major obstacle any more for the next generation of console MMORPGs.
The second problem is complexity. A keyboard has a lot more possible buttons than a gamepad, and it is a lot faster to click on something on the screen with a mouse than with a cursor controlled by a thumbstick. Many a WoW player has 5 or 6 hotkey bars with 12 button each on the screen, which works well enough on a PC, but would be an absolute nightmare on a console. And then there is chat, a major feature of MMORPGs, which would pretty much require console gamers to either buy a keyboard or a headset for voice chat, if not both (you don't want to have general or trade chat on voice, do you?). I think the idea to take a PC MMORPG and simply do a console version of it is pretty much doomed from the start. But a console MMORPG which was way simpler, and worked with a lot less buttons and minimal communication, would be perfectly feasible.
The third problem is the business model. One important reason why there are so many more video game consoles than gaming PCs (not counting office PCs) is that a console is still significantly cheaper than a PC good enough to play modern video games. Hey, many PC gamers have graphics cards that cost more than an XBox 360! That is not to say that console gamers are cheap, but one does have to ask whether selling console gamers a $15 per month subscription will work. A subscription-free business model with microtransactions would probably work a lot better.
So all in all I do think that some multi-million-user console MMORPG isn't all that far in the future. It just won't look and play all that similar to lets say World of Warcraft. A console MMORPG will have more action, and fewer different spells / abilities to use in combat. The combat will be closer to Age of Conan than to World of Warcraft or Warhammer Online; maybe even with automated combos (instead of selecting combo, then do right, right, left, you just do right, right, left, and the combo just happens). Most chat will be mostly based on menus, which also serves to make the game safer for children; only with a keyboard and special permission / password from the other will you be able to chat by typing. There will be a fantasy world, various character classes, quests, monsters, levels, and all that, but the console MMORPG will be free-to-play once you bought the initial game, with optional microtransactions.
For most players of current PC MMORPGs, such a console MMORPG will look like a pale imitation of the games they know and love. But the point of a console MMORPG would be to sell it mostly to people who haven't been playing MMORPGs before. And thus being simpler and cheaper wouldn't necessarily be a disadvantage. Whether that would tempt them to buy a PC and play WoW is anyone's guess.