During a recent interview with GQ, Naoki Yoshida, the producer of Final Fantasy XVI (FF16), discussed the issue of numbering the Final Fantasy series. He mentioned that he has had discussions with Square Enix about the possibility of removing the numerical designations from future titles. This consideration stems from the concern that these numbers may confuse new players and create a perception that they need to play the previous games to fully enjoy the new installment.
To clarify his point, Yoshida also gave an example citing Final Fantasy XIV (FF14), the series' MMORPG. He stated that players might question the need to play FF14 after the release of FF16, which led him to believe that it would be easier for people to understand if FF14 was simply called Final Fantasy Online without the numerical designation. Of course, he also stressed that whether future titles like Final Fantasy 17 or Final Fantasy 18 will continue to use numerical designations is not their concern. Rather, it will be up to the game's developers and marketing team to decide whether or not to continue the numbering.