Never happen. It would be more profitable for them to remake FF1-3 and release them on separate discs. Besides, they already released them for the Wonderswan Color, and they don't care about America, so we'll probably never see this.
They were remaking FF7-9 for PS2, but they put all 3 projects on hold to make FFX and FFXI and Kingdom Hearts. They were going to be on separate discs.
Square expressed interest in making FF4-6 for GBA, but Nintendo probably won't let them unless they make some games for the GameCube also.
In that case, they already remade them for PSX. FF4 is in FF Chronicles and FF6 is in FF Anthology. I doubt another remake for PS2, GCN, or XB because you can play them on PS2 and they won't remake them for such powerful consoles without a Dragon Warrior 4 type thing (3-D graphics, a whole makeover) which would be too costly anyway.
I heard about the wonderswan ports-was this just ff1 or all of them. I'd love to see a GBC (or GBA for that matter) port of FF 1-3, if for no other reason than to get ff 2 and 3 here finally (thus rounding out the FF series here).
There are things that I want to say, but I won't because I'm not sure it'd be considered kosher. And the Wonderswan ports were supposedly going to be 1-6. I think Square was concerned about wedging the SNES ones onto the WS platform which is why they were looking at the GBA.