I haven't seen this pop up on any of the new features with new versions of ACID, and if 11 has this capability please let me know because that would be the one thing I would upgrade for.
ACID can freeze midi, but I would really like the ability to freeze an audio track with plugins on it. Like an update to 'render to a new track' and it keeps the original wav track and vsts and settings saved in the background for unfreezing, but otherwise not loaded so they don't bog things down (and a associated UI update).