Remember the first Jesse event? He gave us nothing, Pegasus and Rainbow Dragon weren't available in the first one. The same'll happen here, we'll get garbage cards that Jack used in the anime or manga and the decent Dragon Archfiend cards will be in a Main Box after Jack becomes playable.
We'll probably get something decent like Trap Eater or Chaos King Archfiend. Jack has a lot of cards. That being said, I also wouldn't be super-shocked if Multiple Piece Golem ends up being his UR...
Jack synchro monster are too powerful. probably the most balanced synchro that he use is just RDA and we all know it will coming from main box so there no chance he will drop Chaos King Archfiend.
Chaos King Archfiend and Exploder Dragonwing are definitely tame enough to be drops. Red Wyvern, Dark Highlander and Celestial Wolf Lord Blue Sirius probably are as well. It's just a matter of what Konami wants to give us.