Adobe labs has released two "pre-production" plugins for you to try out in Lightroom 4. These are not considered finished products, more of a beta-test. (Thus the release via Adobe "Labs")

Here's how they are described on the download page:

• Adobe DNG Flat Field plug-in — a tool used to correct an optical phemonenom called shading, also known as “lens cast”. Please refer to Adobe DNG Flat Field plug-in release notes for additional information.
  
  
• Adobe DNG Recover Edge plug-in — a tool used to recover image data typically lost when using the in-camera crop mode. Please refer to Adobe DNG Recover Edge plug-in release notes for additional information.

Downloads and release notes are available via this page.