Starting next year, Google will provide Chromebook security patches and software upgrades for up to a decade. This will effectively guarantee that no existing Chromebook will expire within the next two years.
However, a Google spokesperson added the caveat that, "In making changes to the expiration policy, we have to coordinate with each partner making any component in these devices. It requires a security and performance guarantee from the makers." Other Google sources indicated that the major Chromebook vendors are expected to work with the company to extend their hardware's lifespan.
They are more like phones than PCs so every model needs it's own specific build and that specific build relies on proprietary drivers