the series has been dormant for 2 decades now, GX on the gamecube was 2003. i don't think it's possible to be deader than it is currently. Nintendo is content to pour all of their racing game ideas into Mario Kart.

edit: come to think of it, this probably is something like a 20th anniversary bit, and they are just going to go back to ignoring it except when they need track ideas for mario kart.