This is how I understood it when I talked to the Firebug team a few months ago. Mozilla has since hired a ton of people for their Dev Tools team and John J Barton has left Firebug due to lack of funding from IBM -- so I have no clue if things have since changed.
tldr; no. Firebug is an independent (but with Mozilla's support and blessing) project and we're also building some great tools that will ship with the browser.
That said, "packages" might be a good idea. The "paranoid package" could bundle adblock, noscript, trackmenot, and foxyproxy. The "developer package" could bundle firebug and anything else that might be useful. Offering binaries with these packages pre-installed from a visible link on the main download page might not be a bad idea.