From the wording in the description it seems like ESO will be one large MMO community. However this is something that no other big MMO has ever done before (that I know of). I know FFXIV did it with ps3 and pc, but never all three platforms. Please let me know if this is indeed the case since it may sway my decision on where to buy it.
FFXI was the only game that was on multiple consoles and pc where it shared servers. PS2, xbox360 and PC but I am pretty sure this will end with each platform having their own community similar to what they did with defiance. If communities do get shared it will most likely be PS4/PC as sony seems a little more open when it comes to their network compared to microsoft.