I have a proposition.
When Gold and Silver came out, there was no female option. Pokemon Crystal eventually introcuced Kris, the first female character option in the series.
Think about it this way. Kris wasn't in G/S, but was introduced in Crystal Version. This theory may be a tad on the "woah, wait, what?" side, but...
What if the female character in HG/SS is a character that will be changed to Kris if Nintendo creates a remake of Crystal? [Remember - IF. Not when, this is a neutral proposition so don't flame me about this."
So that would mean that... whoever that new girl is... will represent herself as an add-in to Gold/Silver [Because they never had a Female Option], and Kris could be introduced into a remake of crystal?