You know, because releasing the same game twice on the same system sounds like a perfect idea!

And the multiplayer in HGSS is far more superior. No fancy emulation technology required, plays online, has infrared support, support for current Gen games. Basically, rereleasing GSC would be too redundant. HOWEVER! A RBY (or FRLG) version on 3DS VC doesn't sound like a terrible idea since those games can't be played on the 3DS.