They are shoving it down your throat now.https://bgr.com/2016/05/25/microsoft-windows-10-upgrade-trick/
You can just generate a genuineticket.xml file, and back that up somewhere, and you will have the means to install it whenever you want
Upgrading and rolling back should work as well.
Faster than Windows 8.1?
by far
how can I upgrade now to win 10?
For free? Not sure if it's possible, but you can try this:https://www.microsoft.com/en-us/accessibility/windows10upgradeRefrain from upgrading to latest build 1607, for now.
You can still upgrade and receive free activation via genuineticket method.Instructions are long, so i'll post it only if requested. did above link work?