After that last set of scenes i'm wondering if Sekai is way less of an existential threat than we were led to believe, she seemed almost like a passive shade, more a memory of her than a real supernatural presence.
Sekai is an existential threat, she's just not the only one.
She's still selfish and not afraid to use other people to get what she wants (like using Kaori to kiss Akira), and with homicidal Ami on the prowl, that's likely to get whoever she posesses in that moment killed.
Her commentary about Nodoka was insighful. It tells us that Nozomu didn't make her the way she was, she was always that way, just like Nodoka. And the fact that Akira sees so much of Sekai in her explains why he continues to put up with her shit.