When will you have to upgrade to Windows 10?

This article is from BT News Tech & Gadgets>Computing and gives an interesting look back at some of the older Windows operating systems as well as their 'best before' and 'use by' dates:

Windows 10: When will you have to upgrade? - BT

Quote:

Windows BXP — Before XP Believe it or not, there are still PCs out there running something older than Windows XP. This tends to be because bespoke software for specific applications demands a particular version of Windows rather than any stubbornness on the users’ part, but it’s not unusual to find Windows 2000 (or even Windows 3.1) running on so-called embedded systems — cash registers, ticketing systems, engineering control systems and so on.

When will you have to upgrade to Windows 10?