They needn't do that, I'd rather see them make a new game including every region, and everything they've come up with thus far... yes, even if you end up with a PokéGear, PokéNav, PokéDex and just about every other technical gadget that exists in their world, not to mention more new Pokemon than the computers can handle. xD Also, custom characters, and full 3D (ever played Dreamfall? Just like in that game :D)... though you'd need something more powerful than a DS for the 3D part... All this, and they can go about adding more Pokemon and regions.
Quite frankly, I'm surprised they've never made what I've just stated above for PC or something.
Having said all of this, yes I do agree with the notion that S/G/C was the best generation, and I'd welcome a remake of it. =]