Even if FFXIV's subscription system doesn't work, the game could join many other Modern MMO's and go F2P. Offering micro-transactions for customers not willing to commit to a monthly subscription usually works out in the companies favor anyway, and it also brings more life into an MMO community. This also works out well for players who choose to retain their month subscription for the additional bonus' that they carry, because now they have more people to play with.
I'm not saying FFXIV will go free to play, just stating that it is an option in the occasion that the player base doesn't bounce back like we hope it will.