Firebug is one of those tools you use and then can never go back to not having again. Awesome to hear a big ramp up in development. I'd be happy to pay for some kind of special version.
On a side note, I think I understand why John works for Mozilla now. I used to think "Damn, John is such a great hacker. Why isn't he just starting startups". But working at Mozilla gives you a chance to really have an impact on the web at a much higher level. Working on a great tool like firebug or planning out new JS language features has a potentially larger impact....your work could be part of the success of many startups!!