I've been running the Firefox latest-betas from upstream for some time (as well
as TBird, and XULRunner)

They're lacking kde4-integration.

I've started tracking this branch to follow the ongoing kde4-integration work
in Firefox.

atm, I've installed

rpm -qa | egrep -i "^mozilla|xul" | sort
 MozillaFirefox-32.99-9.1.x86_64
 MozillaFirefox-branding-upstream-32.99-9.1.x86_64
 mozilla-js-24.5.0-1.1.x86_64
 mozilla-kde4-integration-0.6.4-40.1.x86_64
 mozilla-nspr-4.10.7-1.1.x86_64
 mozilla-nspr-devel-4.10.7-1.1.x86_64
 mozilla-nss-3.17.1-1.1.x86_64
 mozilla-nss-certs-3.17.1-1.1.x86_64
 mozilla-nss-devel-3.17.1-1.1.x86_64
 mozilla-nss-sysinit-3.17.1-1.1.x86_64
 mozilla-nss-tools-3.17.1-1.1.x86_64

on openSUSE 13.1

with these bins installed, after a file download in FF, selecting "Open
Containing Folder ..." does, now, correctly open the Dolphin dialog.

otoh, File -> "Open File ..." and File -> "Save Page as ..." still open the
Gnome/Nautilus dialog, i.e., NOT Dolphin.

Is this a config issue on my end, or still an unavailable fundtion/feature in
the kde4-integration?

fyi, my 

cat ~/.local/share/applications/defaults.list
---------------------------
[Default Applications]
text/html=kfmclient_html.desktop
x-directory/normal=kde4-dolphin.desktop;kde4-kfmclient_dir.desktop;
inode/directory=kde4-dolphin.desktop;kde4-kfmclient_dir.desktop;kde4-gwenview.desktop;kde4-filelight.desktop;kde4-cervisia.desktop;
---------------------------