Nidai Kitetsu plot needs some closing and I can't imagine Zoro leaving Wano with Sandai Kitetsu, that sword is really weak compared to Enma and Kuina's.
Do you think Ryokugyu might destroy that useless sword (Sandai)?
He has a black blade after all and Zoro vs Ryokugyu seems a good matchup for the final arc: both are swordsmen, the admiral seems to have a broken regenerative power, too badass to fight Sanji, ...