I have a 64-bit computer and use Waterfox, the "unofficial" 64-bit version of Firefox (Mozilla has not yet released a stable 64-bit build). There is also Pale Moon, which is built on a lot of the same code and comes in both 32- and 64-bit versions. I'm just wondering if there are any plans to PortableApp-ize other Firefox variants such as these.
http://www.waterfoxproject.org/
http://www.palemoon.org/
Wondering if you've heard also of LunaScape, a rather unique concept: a browser that uses all three major rendering engines (Trident, Gecko and WebKit). I don't see this one on the list and wonder if there are any plans to Portable-ize this one too.
There have been beta tests of both Palemoon and Lunascape in the past. Search if you would like to check them out.
Regarding Waterfox, I doubt we would support a 64-bit only app as this vastly limits portability (the majority of public PCs are 32-bit).
In most cases we don't even portabilize 64-bit versions of the apps that are official, as the positive effects of running a 64-bit version are greatly outweighed by the extra file size of including two versions in the package.
But I am looking forward to the official releases of portable PaleMoon and Lunascape in the future!