One of the additions to Final Fantasy X/X-2 HD is a 30 minute audio episode wherein Tidus meets Auron's daughter. When asked if this could hint at another entry in the Final Fantasy X sub series, Square Enix's Shinji Hashimoto said, "That’s not really our intentions with including the audio episode," and that it was merely an "opportunity for them to include this additional story episode"
Final Fantasy X and X-2 scenario writer Kazushige Nojima has expressed interest in Final Fantasy X-3.
Hashimoto was also pressed about Yoshinoro Kitase's claims that if X/X-2 HD proved successful, it could lead to Final Fantasy XII HD. Unfortunately, Hashimoto responded simply with, "At this moment, we do not have any plans," though he echoed Kitase, saying, "if there are a lot of requests from the fans for a HD remastered version of Final Fantasy XII, we might consider it."
You know what to do, folks. Inundate Square with Final Fantasy XII HD requests.