This has been asked, and theorised and contemplated by so many people and the amount of topics made about it is quite ridiculous.
Chances of a Crystal Remake?
When pigs can sprout wings and take to the skies.
Seriously.
If people check back in the board in the last few pages, there's at least 5 of these topics minimum.
Argument in case:
Why people want a Crystal Remake:
1) To play as Kris.
2) To get the GS Ball and get Celebi.
Reasons there won't be a Crystal Remake:
1) Lyra is technically the same as Kris. Just different hair colour and clothes.
2) Crystal's entire plot and elements such as Battle Tower(and the entire Battle Frontier) are already in HeartGold and SoulSilver.
3) There's no need for a Crystal remake to get a GS Ball because there is already a Celebi event slated to come out soon.
4) Crystal's entire plot and elements such as Battle Tower(and the entire Battle Frontier) are already in HeartGold and SoulSilver.
5) Black and White have already been confirmed as the next games.
6 Crystal's entire plot and elements such as Battle Tower(and the entire Battle Frontier) are already in HeartGold and SoulSilver.
7) The Remakes are following the trend of having no special version, as it's not needed once the remakes have their features anyway.
8) Crystal's entire plot and elements such as Battle Tower(and the entire Battle Frontier) are already in HeartGold and SoulSilver.
Yes, I know I repeated the one point 4 times over.
For clarity.
Point is, there will never be a Crystal remake unless Nintendo is desperate for money and want to milk the success that is HGSS.
Point is, the remakes don't need a third version as any possible features of a third version will be implemented into the two remake versions.
This will be the case IF they create R/S Remakes and IF they eventually remake D/P.