There is an interesting argument to be made for his point of view. Committing to a project with their input might be a good choice for Mozilla's future. However I don't see how Google's grip on the Chromium project can be loosened. As we can currently see with the Chrome Extension Manifest, their arguably profit driven decisions might hurt user freedom. We'll see how Microsoft's involvement will work out and if they can be a counterweight.
Going off on a tangent: the change to Chromium Extension Manifest isn't even that bad outside of them phasing out the webRequest api. One of the proposed features is to have permission settings for extensions analogues to Android App permissions.