Cross quoting:
Yes, this means Suzuka will be graduating from Sakura Gakuin... as expected.
I wonder if they are now going to completely separate Babymetal from SG. Somehow with BM having had their major debut, this seems pretty likely to me.
As far as BABYMETAL's future is concerned I see three scenarios:
1. They could let Babymetal continue to exist despite graduating Su out of Sakura Gakuin. IDZ will probably even break SG's sale record, so killing of BABYMETAL would be stupid. Besides, you can't kill of a group that quickly after a major label debut.
2. However, the IDZ Legend concerts will soon be complete. Actually, that will be on February 1st which is several weeks before Su's graduation from SG. Furthermore, the girls are getting older. So if they were to end Babymetal some time this year it would truly make them a legendary group. It fits their image, since everything has been about "legends." How long can you keep a group like this interesting and groundbreaking?
3. Someone will Replace Su, but I highly doubt this will happen. She's the main vocalist and I don't think the fans would like it either.
(4. Su joins Nogizaka46 to team up with her sister, since being in BABYMETAL isn't a full time job.)