According to this summary, which links to a Tech Report article based on information from the Windows blog, Windows 10 will stop being "optional" on Windows Update early 2016 and become "Recommended" instead.
This means it's going to start installing on even more people's computers automatically unless they lock down Windows Update even further, or disable it entirely. "The upgrade won't be entirely automatic, though. Users do have to accept the Windows 10 license before installation can continue." So that's at least a slim silver lining. But of course if you get to that point it likely means the computer has already downloaded the multi-gigabyte update while you slept.
I wonder how long it'll be before they go from "Recommended" to "Critical".
This means it's going to start installing on even more people's computers automatically unless they lock down Windows Update even further, or disable it entirely. "The upgrade won't be entirely automatic, though. Users do have to accept the Windows 10 license before installation can continue." So that's at least a slim silver lining. But of course if you get to that point it likely means the computer has already downloaded the multi-gigabyte update while you slept.
I wonder how long it'll be before they go from "Recommended" to "Critical".