The debate around the default browser in Ubuntu 13.10 is ongoing, but the Lubuntu offshoot will most likely go with Firefox.
Canonical and Ubuntu flavor developers have started a discussion about the default Internet browser that will be provided in Ubuntu 13.10 (Saucy Salamander).
Lubuntu's lead developer, Julien Lavergne, has made his case on the official mailing list and it seems that Firefox is his choice.
“If I am lazy, the logical choose is to keep Chromium, because Ubuntu (Canonical) already decided to switch to it. So, much of the work from Ubuntu will go to Chromium instead of Firefox. However, many arguments is are favour of Firefox,” stated Lavergne.
Choosing Firefox over Chromium is a strong signal for the other flavors of Ubuntu, but none of the other developers has made any comments in this direction.