1. Pokemon R/S/E already fits into the Pokemon timeline. It occurs simultaneously with the beginning events in Kanto. Remaking it either adds nothing to the story line or just retells it which makes it nothing more than a filler.
2. R/S/E are compatible for transfer to all games 4th and up (and most likely 6th gen).
3. They've made it their duty to add pretty much all Hoenn Pokemon in later games, including all of the wild Pokemon throughout the games, the starters, main legendaries, and the Latis in HG/SS, and the Regis in Platinum and B2W2. However, Deoxys and Jirachi are still R/S/E exclusives, but they're not nearly important enough to make a whole game over it and they sound like Pokemon you could just make an event out of. So it has nothing to do with getting access to the Pokemon.
4. It doesn't have anything to do with the graphics because it it did, there would also be an obligation to remake FR/LG. Releasing them side-by-side maybe? :o
I can't see them making one for any other factor besides money, but to be honest, I can actually see them releasing an R/S/E remake because EVERYBODY LOVES MONEY.
For point 3, I believe that by the end of the entire 3rd generation (RSE/FRLG), all pokemon that were Johto native were obtainable, and yet GSC still got remakes. For point 4, I agree that if RSE gets remakes, that FRLG are bound to get remakes.
Regarding point 2, FRLG made it so that all pokemon that could not be obtained (due to nontransferability), yet we still got GSC remakes. Why should whether or not you can trade between a region be the reason why remakes are being made? If a person really missed the Typhlosion or Lugia they had in GSC, they could have obtained another in Emerald/FRLG. Whether or not a pokemon directly transfered "from Johto" or "from Kanto" on their summary is trivial.
And as for point 1, I think this is one of the strongest arguments against RSE remakes. I think it's very likely that the remakes occured simultaneously with the rest of their generations. But again, I think this reason is trivial to more important reasons.
Do you guys remember how much fans speculated and hyped for a GSC remake right after FRLG was released? I believe that it was the fans wanting them so badly that made HGSS come out. Although there's no where near as much hype from fans for RSE remakes, it's still there. HGSS got the snowball rolling, for more remakes to follow.