They said Odyssey was ending at v25. They could always change their mind, but I was kinda disappointed to hear that. I thought the content was interesting and could've been tiered out further. New T4? T5? It is scalable content as is, but with the v25 update they said it's the last unless they change their mind.
IMO they should change their mind and add Sheol D and new bosses.
v30 would be dumb though, I can imagine they'd have some stupid mechanic like bosses spawn other bosses or fetters auto-KO random players if they are out too long.
v30 fights with Sub Jobs might be fun. Make them Master trial like Content that brings your gear to R31 for epeen. If you beat Bumba v30 you get access Nyamo gear and can make a second set.
Remember when they oops-i-accidentally allowed subjobs in Gaol for like 1hr after an update? I'd be surprised if they didn't experiment with it and that was some test realm leakage.
Either way, I always thought it'd be fun to encourage the climb again. Maybe for doing the whole climb you get a KI that can trade to eliminate some annoying task or expense, like get a Cats Eye or something with higher tier rewards for the higher levels.
I'm sure someone will explain why that'll break everything though.