Many who did upgrade, went for the more conservative choice of Windows 7, meaning that they now face a new upheaval as Windows 10 becomes the only game in town (apart from Windows 8.1 but nobody wants that). For that they might had to https://account.live.com/password/reset Microsoft has already confirmed that the service, which will offer 'Critical' and 'Important' updates (but nothing labelled as 'Optional') will start at $25 per machine, per year, for up to three years. Each year will see the fees doubled.
Users who don't join in the first year will also have to pay accruals if they join later. Prices are lower for Windows 10 Enterprise and Microsoft 365 Enterprise. Also, users need to reset their previous microsoft account, as per the sources here account live password reset.
Failure to keep up to date with Microsoft's timelines can have some serious repercussions as hackers take advantage of unpatched vulnerabilities to spread malware.
Any sysadmins interested in applying for Extended Security Updates should contact their Microsoft account manager or reseller for full pricing.