Playing off Tobold's insights, here are some thoughts of my own on the advent of console MMOs.
First, PC gamers should be excited about console MMOs even if they don't intend to play them. I agree with Tobold that console MMOs will necessarily be different from PC games. Yet they'll still compete with PC games since many, if not most, gamers who own a console also play games, at least occasionally, on their computers.
Any way it happens, the design concepts in console MMOs will bleed into PC MMOs. Each will affect the other design-wise. As a result, we might see more variety in PC MMOs. Certainly, console MMOs will more often focus on real-time combat. That's one feature which will bleed over.
Second, keyboards might not shame console controls in versatility much longer. Voice commands, ala Tom Clancy's EndWar, aren't very popular now, but they will be once a console maker comes up with a more comfortable headset. We could eventually see something as small as Bluetooth earpiece, and voice recognition technology will continue to improve.
All console manufacturers are also making headway on gesture recognition software and hardware. If a console can tell which way you're tilting your controller, which way your body is moving, where your eyes are directed, then that's further control which can be offered intuitively to the player. Advancement of such technology is certain, though intelligent use of it is not. I'm not saying this tech will greatly empower console MMOs, but it could.
Communication isn't a problem, though console communication must rely on voice chat. By next console generation, voice chat will probably appeal to more gamers due to exposure. And voice masking technology continues to improve, so by next generation no one will have to know whether your young or old, male or female, etc. Still, I won't say voice chat isn't without its drawbacks. For one thing, most people are particular about the style and quality of their voice, and those who don't like the available voice masks are likely to not chat at all.
As for payment, I'm sure multiple strategies are possible, including subscription models. People are already accustomed to paying monthly fees on top of their basic subscriptions to cable and satellite TV for additional programming (such as sports packages or movie packages). So paying a fee on top of a monthly subscription to Xbox Live is likely a feasible business model. Of course, Sony doesn't charge for the PS3 online service, so subscription MMOs might be easier for them.
Xbox Live already has customers accustomed to microtransactions, as does PSN. Many people have downloaded additional content for Oblivion, Crackdown, and other games.
Free-to-play models are possible, but I've never seen a free-to-play MMO of the graphical quality that the PS3 and 360 demand. The production costs such quality requires might not make sense for these games. If a free-to-play MMO were released on Xbox Live, I expect it would be released via the Live Arcade.
What other issues might arise in the shift from PC to consoles for MMOs?