My theory for the season finale is that Qo'nos gets blown up or devastated, leaving the Klingons unable to further wage the war against the Feds. They either need to rebuild and terraform the Planet or find themselves another Capital, which they will also call Qo'nos. The hatred against the Federation helps the houses to unite under a single flag again. In the time between Discovery and TOS they build up their forces until they are ready for another war against the Federation in "Errand of Mercy". My theory explains, why the Intervention of the Organians was necessary to stop the war from happening and why the Organians never bothered to prevent another war like the war against the Klingons in the alternate timeline of "Yesterday's Enterprise" or the Dominion War: The Klingons were angry as f... over what happened to Qo'nos and the war might have destroyed the entire alpha and beta quadrants. Clues for my theory might be the destruction of Qo'nos in the Mirror Universe and the differences between what Qo'nos looked like during Enterprise and later in TNG.