I think it's a plausible possibility and a good potential fight. Their are some set-ups.....
- Law helped defeat Doffy.....and Jack wanted to save him
- Jack hurt Bepo's people, and Bepo may wanna fight Jack. Then Law joins in and helps him
- Also Law in Kuri being afraid of alarming Jack....and now fighting him
Yamato defeating Jack feels like it would take too long. And she's needed really soon in the Kaido fight. I don't really see her low diffing Jack. So Law may take him on.
- Law helped defeat Doffy.....and Jack wanted to save him
- Jack hurt Bepo's people, and Bepo may wanna fight Jack. Then Law joins in and helps him
- Also Law in Kuri being afraid of alarming Jack....and now fighting him
Yamato defeating Jack feels like it would take too long. And she's needed really soon in the Kaido fight. I don't really see her low diffing Jack. So Law may take him on.