Final Fantasy XIV was not a successful game, neither critically commercially. The former led to the latter when, after admitting that it was an awful experience, Square Enix allowed people to play it for free. There was always going to come a point when the game tried to go mainstream again and that's just what it's about to do.
Right at the beginning of next year, January 6th, Final Fantasy XIV will go subscription based again and people who had initially decided to pay for the game will be happy to know that, when it relaunches, you'll be saving a few bucks a month. Everybody else will have to choose whether to pay or stop playing, but for $9.99 a month, that's not too much to ask for. There are also other, longer term payments that can bring that price down – $8.99 a month for 90 days, $7.99 a month for 180 – but that depends how much you want to put into the game in one go.
This is in preparation for the 2.0 update which is planned to release over the next 12-18 months.