Ok so we all know that these will be six of the seven half bloods

Percy Jackson - Son of Posidon

Jason Grace - Son of Jupiter

Piper McLean - Daughter of Aphrodite

Hazel - (Unknown God Parent though will definantly be in Roman Form)

Leo Valdez - Son of Hephaestus

Frank Zhang - (Unknown God Parent though will definantly be in Roman Form)

Unknown Half Blood

Ok so here are some theories

Hazel and Frank's godly parents some people think due to the Olympian week thing though i don't think that proves anything. I think Frank will be either a son of Apollo(Roman Form) or Ares/Mars(Roman Form). I think Hazel will be a daughter of either Athena/Minerva(Roman Form) or Demeter/Ceres(Roman Form)

For the unknown half blood there are very many options for it. The one which most people think is Annabeth. Personally I disagree with that and believe Annabeth will just support. Then there is the option of Nico. That seems more likley due to the fact that I think all of the Big Three will have there children as main characters. There is a third option which is Reyna the Roman Praetor of the Twelfth Leigon. I think the Leigon's will be the exact same as the cabins therefore number twelve would equal Dionysus meaning Reyna would be a daughter of Dionysus/Bacchus(Roman Form). Another theory about the Legion's would be the stronger you get the higher legion you get placed in therefore meaning Reyna would be weak and therefore not one of the Prophecy

So there are my thoughts tell me yours