There seemed to be some serious concerns in that link about potential problems from using gstreamer 1.0 in firefox while system libraries are still using 0.1 (as they always will in wheezy).
Even assuming those considerations are resolved somehow that still leaves the question of question who will
1: produce high quality packages for raspbian wheezy for gstreamer 1.0 and the Pi specific plugins for gstreamer 1.0. I know there are some packages out there but has anyone assessed them against debian policy and determined them to be reasonablly sane? Do their build-dependencies represent the boundries in the archive (e.g. stuff in main mushc be buildable and installable using only stuff in main. Stuff in rpi must be buildable and installable using stuff in main, firmware and rpi. Nothing that goes into the main raspbian archive may require stuff from third party archives (and the raspberry pi foundation count as a third party here) to build or install.
2: produce patches against the debian iceweasel packages to use gstreamer 1.0
3: maintain those packages after intiailly producing them for the lifetime of wheezy.
I'm already spending way more time than i'd like looking after raspbian