There's no need for the hold.
If you have 12.04.1 installed you can keep updating it until 2017 and the kernel and X server will still work with your card.
To upgrade 12.04.1 to the new kernel and X server you have to manually opt in to the new enablement stack by running...
Obviously don't run this command as it will update you to the problematic (for your card) 12.04.2 release.
sudo apt-get install linux-generic-lts-quantal xserver-xorg-lts-quantal libgl1-mesa-glx-lts-quantal
More information can be found on the wiki...