The best you could hope for in terms of "improved" graphics is about what you saw with the N64 Zelda games on the GameCube. There's no question that the GC is leaps and bounds more powerful than the N64, but Ocarina of Time on the GC doesn't look like Twilight Princess.
We're going to get maximum resolution out of all these old games, but as for graphical improvements, not really. They'll just run better on the Rev hardware, provided the emulation is solid.