I had already read about plans for FireFox v.3 and it is not surprising everyone is looking ahead, not just the population of the Mozilla Foundation. Specific information is hard to find, now, but will almost certainly surface in the next couple months.
I am in the process of writing an article in partnership with my friend, Waleed, about spreading literacy, computing and information technologies to developing nations using the so-called "Web 2.0" technologies. Along the way, we have decided that in order to increase efficiency, the current web browsers need to morph into web browser/application browsers. While related to the web browser, the application browser additions make the application browser a different species, however close their common ancestors are.
I suspect that web and application browsers will not separate into differing programs. They will remain united. It doesn't make much sense to code up separate application in this case, generally speaking. There may be exceptions, though, such as security needs, that will dictate a separate application. We will just have to wait and see.