A debate is currently ongoing regarding long-term support of Firefox, with some surprised that Firefox 4 is being EOL'ed, and what that means for the viability of Firefox in the enterprise, if Mozilla is going to release a new version every 6 weeks.
Without stating an opinion either way (since I don't have one), there is one potential solution here that I haven't seen mentioned enough. The whole point of open source is that anyone, anywhere, can take the source code and customize it for any purpose they see fit. If there is indeed a need for long-term support for Firefox in the enterprise (and again, I am voicing no opinion on the matter), then anyone can do that. It doesn't need to be Mozilla. Anyone can form a new company, do the work to backport security fixes and QA them, and sell long-term support for Firefox (or this could be done in various other ways).
This is possible since Firefox is 100% open source. It isn't possible with proprietary software like IE, and isn't possible with software that mixes the two (like Chrome: you can sell long-term support for Chromium, but it will not have Chrome-only features like print preview, etc., so it would be a different product).
I want to stress the fact that you can sell open source software. Complying with Firefox's license doesn't preclude that. I won't get into the details, but this model works fine, just ask Red Hat. In fact I assume Red Hat already does exactly this, it sells supports for old versions of Firefox as part of Red Hat Enterprise Linux for a very long time.
Mozilla is driving Firefox forward as fast as possible, but Mozilla doesn't 'own' Firefox in the sense that it is the only party that can do things with it. Anyone can. If there is a business need for long-term support for Firefox, anyone can serve that need by selling that support.
Note that this is not a case of me saying "if you want some feature, you can always do it yourself". The situation we are talking about here is enterprise users. Big corporations do pay for support for the software they use, it is worthwhile for them to pay for such support. My point is that open source software like Firefox fits into this model perfectly - if there is a business need, anyone can step in and fill that need.
Again, I don't have an opinion myself as to whether such support is important - I don't know enough about the enterprise software market to have such an opinion. I also have nothing to do with Mozilla policy and planning, I just write code. My only point is that Firefox is open source, and that means it is business-friendly in the sense that you are not under the control of a single vendor selling you a product: You can customize the software yourself, or you can get someone else to do it for you. As an open source advocate, I wanted to point this out, since Firefox is the only major browser that is 100% open source, and that means there are solutions to a situation where people say there is a need for something, but Mozilla does not currently do that thing.