I kinda am unable to see the Massive part or the Multiplayer part most of the time and i especially lack to see the combination of both. On the other side, my standards might be slightly off because i am used to Eve and its version of massive multiplayer that involves hundreds (even thousands) of players slugging it out.
Mobius alone has nearly 40 thousand members playing ED. The instancing in this game tends to hide how many people are actually floating around. The CGs in LTT 377 this past weekend had nearly 10 thousand individual contributors for the trade one, and I think nearly 11 or 12 thousand for the combat one.
Not sure that there was ever a hard number put on the definition of 'massively multiplayer', but we've a fair number of folks playing the game as a whole, which should increase once the PS4 release hits.
I think what a lot of people tend to overlook is that this game operates on multiple platforms, in multiple modes, which don't always allow you to see just how many people are actually there. Unfortunately, the choice of networking and instancing is likely going to prevent us ever seeing things on the same scale as you'd see in Eve or other similar games.