Some great developments
Indeed many things would change and all it would take to bring the game down would be having a shitload of nondepositors consuming all the bandwith like Alphageek said.
Its interesting to see that while
MA might want a big database of players, they have to meet certain conditions, otherwise it might mean bankrupcy - having the servers for all those non depositors, f.ex.
Also like auktuma said, content and things to do would have to be deeply revised.
EU has no quests, therefore it could get boring really fast for many players.
The market would also be flooded with crafters fighting for single peds to earn a living.
So far, i think some very clever answers
Personally i think that with all those players, the game would probably sink all together, economy wise.
MA would have to make instances of the areas in different servers, much like WoW does it to keep up with all that traffic. That means the populations would never reach high levels in a single server. So Hadesheim would still be empty.
Also, in some servers you would have high end items, on others you wouldn't. Who would want to play in a shit server? Can't imagine mod faps dropping in each individual server.
Balancing loot would also probably become a nightmare, to keep track of everything and not allowing any "leaking ped holes".
And so much more...
Perhaps
EU is not tailored for a mass public, but for a selected thousand. The efforts required to maintain such a demanding database of players would probably be too much for
MA to handle, with the current game setting they have right now.