?
Maybe some spoiler here.
Jin kills his uncle in canon ending.
There is no more samurai hunt after because well you killed the boss that ordered the hunt... the castle is closed after uncle dies.
The 2nd Monghol invasion could be used as a new game but it should not be Jin anymore because he didn't have any purpose to even fight in that invasion at all.
But I believe it was choose another period and location... one 300 years ahead because it add way more to game mechanics than a second Monghol invasion.
Jin story ended in Gosth of Tsushima... even the theories about the 2nd Monghol invasion questioned who will be the protagonist.
He became a criminal and is wanted for the murder of his uncle, so he actually became a fugitive.