New version of Firefox 3.5.x released.
Will updating my Firefox Portable from previous one (also 3.5.x) by copying
manually all binaries from local installation to the portable installation?
The question addresses all updates within the same major version.
With 3.5 and up you can just use FF's built-in auto-updater to update Firefox Portable. There used to be issues with doing that, but it's safe to do now.