Star Citizen

Star Citizen Crowdfund Pitch - 720p from Roberts Space Industries on Vimeo.

Star Citizen is a game developed by Chris Roberts, creator of Wing Commander, Freelancer, and Privateer. To me, this seems like the better of the two space-themed sim games coming out in 2014 (at least, in comparison to Elite: Dangerous). From watching videos of the two, the combat appears much more fleshed out. In any case, the premise is simple: you are the pilot (or an inhabitant) of a space craft. There are three modes to play in: single player, in which you play Squadron 42 missions reminiscent of Wing Commander; private servers; and the official server.
Rather than likening this to an MMO, as a specific image is conjured by that term, I'll simply describe the gameplay, paraphrasing the information Chris has given:
As a pilot: You start as the pilot of your chosen spacecraft. You load up cargo, expecting to sell it to a neighboring planet. You take off. En-route, the game decides you will have a combat encounter. At this point, you leave the main server, into an instance, in which you and your friends have a chance to fight the encounter. You can pull friends into open slots on your ship, or your friends could fly their own ships in to join. You resolve the combat, and then go back onto the main server, where you complete your delivery or sale.
The non-pilot mode has me interested, though. You can sign yourself up as a mercenary to be used in space combat and boarding actions, and can play through as if you're a player of a FPS, or join in to a dogfight via an on-board fighter. This in my mind is what sets this apart from other space sims.
All told, this is certainly on my radar, come next November.