How many old characters should we expect from Battle Tree?

12 in total? One champion - one rival from each gen?

Red - Blue
Lance - Silver
Steven - Wally
Cynthia - Barry
Alder - N or Cheren (or Bianca cause not so much females)
Diantha - Serena (if there's any other protagonist with a chance to appear its her) or Shauna

Thats all i guess?
Wouldnt count on gym leaders seeing as this is just a Battle Tower/Subway/Maison copy