Pokémon Card Set Timeline

It would be fantastic to predict the release date of the next Pokémon Trading Card Game set. While sources like PokéBeach reveal upcoming set names several months in advance through trademarks filed by Pokémon, I'm also interested in identifying any patterns in the release schedule. I've compiled a table with the release dates of all the sets so far and hope to provide some valuable insights.

Key Observation From Japan Release Schedule

In general, from the table below, we can find a strong pattern of the Japanese set releasing.

■Three years for a generation

There are 3 types of sets: (1) "Main set" sometimes can be released as a pair. (2)"Augmenting set" comes after a main set and marked with "a". (3) "High-class set" comes at the end of every year, usually containing most art rares and replicates of useful cards.
Sword & Shield, Scarlet & Violet eras: ■ Main set: January, April, July, October. ■ Augmenting set (a): [February, March], [May, June], September. ■ High-class set: December.
Since Sword & Shield, August has always been empty for the releasing schedule. Potentially to make space for the World Championship in that month.
New gammick (Single/Rapid Strike, VSTAR, ex, Tera ex, ACE SPEC) comes every January. Others have been unstable. For example, V/VMAX (Dec 2019), Amazing Pokémon (Jul 2020), V-Union (Aug 2021), Fusion Strike (Sep 2021), Radiant Pokémon (Feb 2022), Lost Zone (Jul 2022), Ancient/Future (Oct 2023).
Sun & Moon era: ■ Main set: December, March, [May, June], September. ■ Augmenting set (a): January, April, February?, May?, July, August?, October?. ■ High-class set: [October, November].