Of course its not the be all and end all, but its the major indicator for a games success out of the gate. Day 1 or even week 1 playerbase counts dont matter, its usually much after that shows if people are willing to play it at its current state and stay. Patches and updates exiat for those who stayed to have more content and potentially drive more users in, but for a strictly online game especially one that touts 128v128, keeping a sustained playerbase initially matters a lot for momentum.