To clear things up, DSi isn't a rumor anymore, nor is it the next hand held console from Nintendo. It's merely an upgraded DS with a larger screen, better speakers, music playing capabilities, better WiFi, and a built-in camera. Aside from making games that would utilize the bigger screen and camera, it's not an advancement in the power of DS games. That said, I'd say that if a G/S remake is released, it will be on DS/DSi, not the next proper hand held.
Anyways, I think the next Pokemon games announced will also be spin-offs, probably Wii related. Possibly PBR 2? Or maybe the first Wii based Pokemon RPG. It could even be PBR 2 with a scenario mode the same way that Colosseum functioned. Barring that, I could see a new Pokemon Snap-like game announced, especially after they released Snap onto the Virtual Console. Something like that would play perfectly with the Wiimote.
I also wouldn't put a Mystery Dungeon Wii game past them.