X is the great leveler of UI. any toolkit can be used. likewise, any app can control/talk-to any other app in any language with DBUS. this is the diversity that only Nokia and OpenMoko managed to ship.
I am not sure diversity of tools is key to survival in this space. Android is proving very successful right now and does not even include X.
http://soundcloud.com/unaudible
Nokia will not be able to achieve critical developer mass faster than Android and will soon be unable to compete.