Microsoft has once again extended its free Windows 10 upgrade offer for customers using assistive technologies. Despite the company saying last year that the accessibility upgrade offer would expire on December 31, 2017, the dedicated website has recently been updated to mention a January 16, 2018 expiration date (via MSPoweruser).
To take advantage of this offer, Windows 7 and 8.1 users have to download the Windows 10 installer from this page, and Microsoft won't actually check if you really use assistive technologies on your PC. January 16 is less than two weeks away, so you'll have to act fast if you want to update your PC for free.
If you do use assistive technologies on your PC, Windows 10 does come with many new accessibility features: among highlights, there is a Narrator that supports 27 languages, reading-friendly fonts, support for advanced voice commands and even built-in eye tracking support. You can learn more about all the new accessibility features in Windows 10 on this page.