I’m not Melody (and she’s not here right now!) but I think I can answer this one.
Spring gold will never be a regular production color. It’s a special, “artist’s edition” color done by one specific painter. It’s too complicated to reproduce for a regular production piece.
There will probably be other molds done in this color, however. There just won’t be very many of them, they’ll all the the “artist’s edition” type of figure, open ended, done in small numbers, etc. as described in the secret keeper auction.