I turned off Windows update because I read about problems with BIOS tinkering within the updates. Partitioning is not something I do on a daily basis so fear has been creeping up on me with updates to Windows and Ubuntu. So to clarify, if the Windows 10 "upgrade" affects GRUB2 and screws up my dual boot, will the partions I created stay? In other words, if the Windows 10 update corrupts BIOS or GRUB2, is there a way I can check if there are partitions that have not been corrupted?
Who knows? It's the best part of a year away.
The reason I'm answering this rather than voting to close is because even though we don't know yet, it doesn't really matter. Even if Windows Calculator deep-fries GRUB every time you use it, the answer is the same: just restore GRUB.
Windows will always do what Windows wants to do, just learn how to cope with it.