I'm sure the booking of the venues for 2023 was already finished before the show in 2022 took place. So the lack of Athen in 2023 wasn't a consequence of poor ticket sales.
I know bands that know their tour plans two years in advance, or start booking venues that long in advance. Therefore, I believe that a band of the size of Maiden can look ahead several years and know what is planned for, say, 2028.
This whole COVID situation has certainly thrown a lot of things into disarray, and I've been wondering for a while what Maiden's tour schedule would have looked like without COVID. Would there have been a 'pure' Senjutsu tour (without) SIT in 2021/22? What would have happened between a Senjutsu/TFP tour and the anniversary tour?