It's pretty obvious Jesus Burgass and Luffy is going to win their blocks, so these are my guesses:
Block A: Jesus Burgass
Block B: Bartolomeo
Block C: Monkey D. Luffy
Block D: Don Chinjao
I don't think Rebecca is going to win actually. I can imagine her being defeated in some kind of unfair match, which will make Luffy furious.
On the other hand, our "Prince" Cavendish is going to fight against Luffy in Block C. Also, during the fight, I can imagine he's going to be violently punched in the face by Luffy, losing his charm in less than a second.