There have been a LOT of rumors surrounding the Nintendo NX platform, the upcoming console/handheld/hybrid/something? from Nintendo. With the exception of a few patents that may or may not be related to the NX and quotes from people who claim to have an inside track to NX development, there's very little in the way of solid information about how the NX will shape up or even what it actually is.
The latest rumor claims that the NX might get a couple of major launch titles in the form of both the upcoming Final Fantasy XV and the highly anticipated Final Fantasy VII Remake. This should obviously be taken with a huge grain of salt, but the originator of the rumor does have a decent track record with game rumors and there are a few bits of evidence that make it at least possible - even if it doesn't seem likely.
The information comes from YouTuber SuperMetalDave64, who claims to have a source who is not a developer on either game but has supplied factual information in the past. According to the video, both of the Final Fantasy games will be ported for release on the NX and those ports are likely already in development. Given the release timing, at least Final Fantasy XV would likely be a launch title. The ports are rumored to possibly be definitive versions of the game as well, since the NX is apparently once again rumored to be more powerful than the PlayStation 4 (and thus the Xbox One as well.)
While the idea seems kind of unbelievable at first, it's not entirely outside of the realm of possibility. Final Fantasy XV is already confirmed as a multiplatform title, so having an NX release added to the PlayStation 4 and the Xbox One isn't exactly a stretch. Final Fantasy VII Remake is a PS4 exclusive, though the developers have commented in the past that they would be open to expanding it to other platforms. If you add in the inclusion of Final Fantasy VII's Cloud as DLC for Super Smash Bros. as a sign that things are at least somewhat friendly between Square Enix and Nintendo, plus Square Enix reportedly already having development kits for the NX (and confirming an interest in developing for the system), then it's at least possible that we could see at least FFXV released on the platform.
Of course, "possible" doesn't necessarily mean "likely." Still, high-profile releases like Final Fantasy VII Remake would go a long way toward driving interest in the Nintendo NX and would be a big show of third-party support for the new system. This is definitely needed to spur sales for the NX, since the Wii U's underperformance is often attributed in part to a lack of third-party titles like Microsoft and Sony enjoy.
For now, though, one shouldn't make plans to play the Final Fantasy games on the Nintendo NX just yet. We don't even know when the NX will be released, what form it will take or what the system's hardware will be like. More information on the NX is coming later this year, possibly within the next few months, and that will hopefully start to shed some light on what it's capable of and what sort of games we can expect on the new platform.
Final Fantasy XV is expected to release on the PlayStation 4 and the Xbox One later this year, with a release date reveal planned for March. Final Fantasy VII Remake is currently in development with no definite release date as yet. The Nintendo NX platform does not have a release date yet, though details about the system will be released later in 2016.