"Bleach" chapter 680 follows Isshin and Ryouken as they cross a portal that allows them to be right where Ichigo and Uryuu are. After crossing the portal, Isshin tells Ryouken how thankful he is of his father.

Avid fans of "Bleach" speculate that the father of Uryuu and Ichigo will appear in the next chapter, and here are the possible reasons why.

In the earlier chapter of the anime, Souken Ishida lent both of them a device that allows them to create a portal and go to a different realm. It was the same device that allowed the father of Ryouken to flee from the hidden realm of Quincy.

Spoilers for the chapter suggest that as soon as the fathers arrive, Isshin and Ryouken will part ways to help their own sons. Isshin is speculated to fight Yhwach while showing his Bankai, while Ryouken will confess something of importance to Hashwalth.

It is also speculated that Inoue will heal Ichigo so he could regain his strength and join his father in his fight. Getting extra help from both Inoue and Ichigo, the best possible result would be them taking Ywatch down. While fans believe that it will not be that easy because of Ywatch's ability to change the future, the father and son's brute power can suppress this ability.

Fans believe that if activated, the time alteration ability of Isshin's Bankai can negate Ywatch's ability to see the future. If Isshin alters time, then Ywatch will no longer be able to see what Isshin's next move will be.

It has yet to be revealed in "Bleach" chapter 680 if Isshin and Ryouken's arrival in the other realm will have an impact on the ongoing battle.