Tsukasa is kind of already important, so I am definetly looking forward for her events.
Speaking of wizard stuff and out-of-air theories, I am currently under impression that Maya was Sekai student/relative/both. Not only because of things that everybody knowns and ignores, but also because of some untold linkage between Sekai's poetry and way Kumon-mi currentlly works. It also would be interesting to see some Maya/Wakana dynamics if Maya would somehow known that Wakana is prying specificaly into stuff that might destroy Sensei
I guess the wakana discovery is more relevant for ami...i think sensei is her real father and i dont believe it was a simple accident that killed sekai and his brother...
Another theory of mine pertains sana...the visions her mother described, the visions she had herself and the thing that possesses yasu regularly sound awfully similar. Her dad was a teacher like you, he fucked her mom, impregnated her and fucked the next. Same lifestyle. Would ayane suffer similar visions without the reset? I mean, akira also has pretty messed up visions and blackouts with perverted consequences...and just like sana he triggers yasus "demonic" side, a side noone else witnessed so far. I wonder what happens if yasu and sanas mom would talk...or if ayane could trigger it as well.
Sana, her mom and yourself try to fight this influence, yasu is so open to the idea of being the vessel for her god, she dont even realises when she get used...but what if sekai had it in herself too and wrote about it? Her poetry couldnt be related to the reset stuff, noone would have been able to read it (aside from he rooftop squad) and we learned from makoto what happens when one of our girls dies, so it would only make sense if she died before the resets began.
But considering all the useless advertising bullshit, we could also just wake up in a nuthouse with a tv addicted roommate when we miss a reset...