Multiplayer, in any form, will not be implemented for a very long time. Even then, it is unlikely it will ever support more than 12-24 players on a server so an MMO is pretty much out of the question I recon.
PC SPECS: Windows 7 Professional 64-bit, AMD Phenom X6 1100T 3.60 GHz CPU, NVIDIA Geforce GTX-680 2GB GPU, G.SKILL 16GB DDR3 1600 (PC3 12800) RAM