Here is more evidential proof on why a Crystal remake may not come to past. For one, like so many have said before, when FRLG came out, a Yellow or even Blue remake never came to follow. To add onto this idea, HeartGold and SoulSilver has been confirmed to see the Battle Tower in the exact route where it was located in Crystal. So, with this being said, if there were to be a Crystal remake then more than likely the Battle Tower would have at least been kept for Crystal like before instead of probably being placed in the main GSDS games.
Now, even if the possibilities of a Crystal remake are low, I wouldn't count out seeing some Crystal references placed within the game. For instance, besides the Battle Tower we have also seen from the Johto Map the same lodge where Suicune was in Cianwood City I believe it was. Not to mention, if we had Shiny Gold as a ROM, then at least one person out there will take the chance at a Crystal ROM hack.