Crazy or reasonable fan theories about The Last Daughter go here
Taylor will meet her Kryptonian relatives of The DCU
At some point the barriers between dimensions will weaken and she'll visit the DC universe and meet with her biological father Superman and his cousins Supergirl and Power Girl. Or they'll be introduced to her. And we'll possibly have a scene where Rachel will play fetch with Krypto.
Taylor will become a Red Lantern for a short while
At some point someone will drive her mad enough to draw a Red Ring...Superwoman: (pouncing) Congratulations, <insert name here>! You got me in the freaking wrong day!
... and suddenly Scion will remember he has to attend an urgent appointment out of the planet (and solar system).