GENERALLY, they release the dates about 18 months out. Historically (prior to COVID) this is what happened:
"Winter": first cruise in the new year up to April/May (not including spring Panama Canal and Transatlantic) – sometime between late September to early November
"Summer": cruises from about May to August/September (not including fall Panama Canal and Transatlantic) – mid February to early April.
"Fall": September until the end of the year (ending with the last cruise starting in the old year) – generally around May.
So, I wouldn't expect fall cruises to show up before late spring.