It would appear that Microsoft has now gotten even more aggressive in trying to push Windows 10 upon people. The opt-in box that people have been seeing has evolved into a new pop-up with a specifically scheduled date that the upgrade will occur unless you opt out:

If you're one of the many who are wishing to hold off on "upgrading" to Windows 10 (for many legitimate reasons), it's critical that you click on the "Click here to change upgrade schedule or cancel scheduled upgrade" link to avoid having the migration to Windows 10 forced upon you.

Many of my clients have hired me to make some adjustments to their computer to block and thwart Microsoft's ongoing attempts to make them get Windows 10. If you're interested in this, please let me know. It is a short amount of work though so I'd advise combining it with other things you might like to have me assist you with.