Google has begun testing their upcoming extension manifest manifest V3 in the the latest Chrome Canary build. With this initial ‘alpha’ release, developers can begin testing extensions under the upcoming specification. Google expects the manifest v3 to go live in 2020 with the v2 end of life to be determined in the future. The most controversial aspect of the extension manifest is the upcoming changes to the webRequest API. Google has created a Migrating to Manifest V3 guide that developers can use to migrate their existing extensions.
Source: https://www.bleepingcomputer.com/news/software/google-begins-testing-extension-manifest-v3-in-chrome-canary/