I never thought of that....
No, they will be probably the exclusive Pokemon mascots.
I would like if they became Water/Light, Water/Dark or if their final form was Dark/Dragon Light/Dragon.
The new region could be next to Hoenn or Sinnoh.
Look at this: https://i672.photobucket.com/albums/vv90/Grave-Lala/Album Covers/japan3.gif
Rainbow would be my preference but the names is most likely copyrighted already and I don't think Rainbow is...
So basically instead of repeating a bunch of other peoples ideas I just quoted them. All those quote caught my eyes as awesome or likely possibilities. In my mind at least. Meant to quote BobandBill too but whatever, I've got enough. :P