You do realise there will most likely be an optional sub, there is always players that sub to games for the extra benefits, even if only 10% of current numbers keep an active sub that should generate 2 million plus a month, combine that with micro transactions for people that want to but UEC and cosmetic items and that will be more than enough to put out content and keep the game running.
Also there will be a number of players waiting till the game is released before buying.