Re: Final Fantasy IX - "This is an age-old ritual between friends!"
A PS4 version might not be so farfetched, but I think it'd be contingent on the sales of the FF7 port and a subsequent FF8.
This may be, but to my knowledge, [which has already been wrong, but whatever...] the PS4 has a harder time emulating older games like the PS1 for having different technology in it. The PS3 was capable [which is why all three are available on PSN, but even then suffers frame rate issues and weird other things], but the PS4 has a harder time.
I'm not sure what they'd need to do to make it available.
As for the 3DS, I still don't see it happening. If it does, VII will most likely come first out of the trio, maybe after something happens for V and VI, which for whatever reason has not happened. [or has it? i'm out of the loop, something may have happened for V]
So we would not see such an expansive port for a very long time outside of general hacks and rooting of the DS software. It may be able to handle it, considering games like Xenoblade and Monster Hunter and whatnot exist and work on it... Buuuut legal limitations, contracts, etc. could still get in the way of it happening right away.
Final Fantasy in general has shied away from Nintendo for years since VII brought such an impressive and iconic moment for Sony. But Square-Enix is also now working more with Nintendo than before with the amount of handheld remakes, Theatrhythm, Bravely Default, etc. And of course, Cloud's entry in Smash with the amount of care and small details he had, I do not doubt that they were talking to them for a while... It's hard to say, but I'm remaining speculative on anything happening past Final Fantasy VI for a 3DS release.