The problem will be the same as when FFXI hit X-box and PS2. The graphic's limitation of the systems (PS2 in this instance) prevented them from ever updating the graphics, the direct X system, and the resolution when there was plenty of opportunity to. Keeping in mind the older engine that XI ran on was not modular and therefore harder to tweak. This they noticed slowed their growth in the PC market as newer and next gen graphics cards came out, and prevented the release on PS3 (except on the backward compatible models).

I believe with FF14 that there is an effort to keep such flexibility alive, but with the PS3 graphics not yet topped out, and the 360's already peaked I don't believe they will port it to X-Box 360 at all. With the U's jump to current gen graphics It is not out of the realm of possibilities to see it get ported there. However the U's ultimate performance both offline and on have yet to be fully tested/realized, and then there is the issue with coding differences and the fact that Nintendo is focused on interactive motion games.

Best bet, /if/ X-Box get it, it will be on their next gen console. Wii-U /may/ see it but not i would say for at least a year.

That being said, with the new graphics engine being more modular than that of XI's, it is possible that they will follow the lead of several other long long running MMO's such as EQ and EVE, and create "Optional" graphics engine updates. The option to use better modeling, shaders, etc would allow computer users to continuously tweak their systems for the best visuals available while not making the console update beyond design limitations. This shift would allow them to span any and all consoles in that aspect. The only issue being that certain systems would have to accept lower resolution graphics and/or the machines would be working flat out.
So the possibilities are out there, but unless SE has had this in mind since the beginning of building the current engine it will take a long time to get it tweaked for porting.