Mozilla acknowledges that their new built-in development tools for Firefox 4 will have "more design and development resources than Firebug" along with the advantage of being built into the browser.
The Firebug blog explained the new situation the project finds itself in:
Our little Firebug project must adapt to this reality if we want to continue to make a difference. With no doubt, the Firebug team can take credit for changing the world of Web development. Now can we avoid becoming a victim of our own success? Simply working harder to compete is equal to giving up. Instead we have to raise the bar!
Old Firebug Logo
So what is Mozilla planning? First, Mozilla is going to make the tool available for other browsers, including mobile ones. The internal systems will be reorganized and put into new wrappers. Firebug's back and front ends will be separated and the code bases for Firebug Lite and Firebug-for-Firefox's front end will be merged.
The biggest change will be the requirement for greater community contributions. Mozilla intends to have increased collaboration with the project community in Firebug core and extension development. They are also asking users of Firebug to donate time or money "in proportion to the impact Firebug has on their work."
A new era of Firebug is beginning.