Personally, I've heard both proposed before. How about gameplay similar to the current GBA offerings, with gameplay similar to stadium during fights? Would be pretty cool.

I would like to see a 3D Game on a handheld like the DS, that would be cool, but it would be too much, the 3D graphics would take up half of the space for the game and the other half would only be half the game, the battles would be shabby, the triners wouldn't be fully developed, neither would the pokemon, thats why they do it in 2D