With key members having already graduated, what will happen to old SKE unit songs/7-nin senbatsu songs? Now that Furukawa Airi and Yamada Nana have left SKE, what will happen to Manazashi Sayonara in future performances (such as Request Hour)? For Aozora Kataomoi, 4 out of 7 original members have already graduated. Will the song be no longer able to be performed with 3 remaining original members + replacements? What will happen to the units now that some of the original members have graduated?
The songs will be performed with new members. Nobody owns a song in the 48 universe, everything will be re-done by other people.
They'll be replaced like always. I don't know why people think that some songs are property of certain member, like when people were saying that they should stop performing Heavy Rotation after Yuko leaves, lol. No, these songs are property of the record label and/or whoever was involved in writing and producing the songs, they have the right to do whatever they want with it. Some members happened to be chosen to sing it and some songs may even be written with them in mind, but it's still (officially) an SKE48 song first, and (unofficially) a Furukawa Airi song second.
Uh, ditto what everyone else said! Songs will continue to be performed regardless of who graduates. For request hour, it's always possible that graduates will return to perform the original lineup. But after they went all out at this year's RH, I kind of anticipate we'll see fewer grads next year. Although Kitarie will still show up for Tsuyogari Tokei, any place, any time, until the end of 48.