Wireless? I smell item trading (generally the easiest thing to implement, I think). A jet bike race should be fairly easy too (didn't they already release just the bike race in Japan several years ago?). A SoM style combat system would be fun, but it would really need to overhaul the combat system then.
Touch screen? Probably just the menus (in and out of battle), but I could see certain attacks (like Flame Toss) going only in the line that the stylus draws. Maybe characters can actually move around the battle field too; that would be nice.
As for the new dungeon, it probably is a "secret" dungeon that will have no effect on anything else in the game (thus probably no Singing Mountain, northern palace, etc). It would be incredibly if one of the missing areas was restored, but that seems like a lot of work for a re-release. I don't know if Square has it in them. Still, one can hope.
