Chris Lord is hoping to generate enough interest in making it easier for Gecko to be embedded into use-cases like a game's embedded user manual, a third-party browser with native UI, web applications, OAuth authentication UI, and other possible scenarios. Right now, Gecko can't be easily embedded while Google's Chromium CEF (Chromium Embedded Framework) tends to be widely used by many different projects.
While CEF is dominating, Lord is making the plea to have more work be done on an embeddable Gecko. He wrote in the blog post, "If we want to form the basis of the next big thing, it’s not enough to be experimenting in new areas. We need to enable other people to experiment in new areas using our technology. Even the largest of companies have difficulty predicting the future, or taking charge of it. This is why it’s important that we make easily-embeddable Gecko a reality, and I plead with the powers that be that we make this higher priority than it has been in the past."
At least regardless of what happens with Gecko, Mozilla's next-generation Servo code-base has already been working on compatibility with the Chromium CEF API.