The new policy applies to any Surface PC shipped after January 1, 2021.

Surface devices shipped before that date will still get four years of firmware updates. This means Surface Pro 7+, Surface Go 3, Surface Laptop 4, Surface Laptop Go 2, Surface Studio 2+, Surface Laptop Studio 1 and newer have benefited from the two-year extension.

Previously, Microsoft had only said it would support devices with at least four years of those updates from when they first came out, as you can see in an archived version of the document.

According to Vole, devices released before January 1, 2021, will get driver and firmware updates for at least four years from their release date. If the support duration is longer than four years, an updated end-of-servicing date will be announced before the last servicing.

Devices released on and after January 1, 2021 will get driver and firmware updates for at least six years from their release date. If the support duration is longer than six years, an updated end-of-servicing date will be announced before the last servicing.