The script for the second season of the famous Shogun series has already been written: there will be 10 episodes in total

After the successful first season of Shōgun, based on the novel by James Clavell, FX and Hulu have officially confirmed the second and third seasons. Hiroyuki Sanada will reprise his role as Lord Yoshi Toranaga.
Here's What We Know
The series co-creator Justin Marks noted that the second season will be "darker" and will dive deeper into historical events, in particular, Toranaga's rise to power.
Although the release date of the second season has not yet been announced, it is known that the script for season 2 has already been fully written, and there will be 10 episodes in total.
The series tells the story of the English navigator John Blackthorne, who finds himself in feudal Japan in the early 17th century. Blackthorne becomes the first Englishman to be appointed a samurai and finds himself in a whirlwind of political intrigue, power struggles and cultural differences.
Shogun has won various awards, including an Emmy, Golden Globe and Peabody. On Rotten Tomatoes, the series has more than 85% freshness.
Source: Deadline