Note: All credit regarding this information leak goes to XOF.
Among these, are cards owned by the protagonist Jaden Yuki and other prominent characters such as Aster Phoenix, Chazz Princeton, Alexis Rhodes and Bastion Misawa, meaning that they might be the first unlockable characters once GX is added. The datamine also shows the rarity of some cards and how duelists could get them.
Zane is a powerful duelist from GX series, his deck is themed around Cyber Dragon and it's other forms and fusions, his deck then centered around both Cyber Dragon and Cyberdark later on in the series.
There are enough fusion monster cards and substitute material monsters in the game you can get polymerization easily from leveling up joey or get it from the trader and if you run out of your 3 or less copies of polymerization ever heard of spell reclamation and getting rid of your own monsters to make space is easy as hell tribute summon, econ, tttd etc. This is not a challenge