The Lightroom team has announced the availability of the official versions of Lightroom 4.3 and Camera Raw 7.3. This free update to Lightroom 4 contains support in the Library and Develop modules for the new HiDPI monitors (i.e. Apple’s Retina Display), bug fixes, support for new cameras, and new lens profiles (including for the iPhone 4s and iPhone 5).
I would encourage you to do this update. Depending on how your Lightroom 4 preferences are set, Lightroom may or may not prompt you to update. If it does not, go to Help>Check for Updates. After the file downloads, double-click on it to run the installation wizard.
Here’s a list of new cameras supported:
Canon EOS 6D, Canon PowerShot S110, Canon PowerShot G15, Canon PowerShot SX50 HS, Casio Exilim EX-ZR1000, Casio Exilim EX-FC300S, Leica M-E, Nikon 1 V2, Nikon D5200, Nikon D600, Olympus PEN E-PL5, Olympus PEN E-PM2, Olympus STYLUS XZ-2 iHS, Panasonic DMC-GH3, Pentax K-5 II, Pentax K-5 IIs, Pentax Q10, Sony DSC-RX1, Sony NEX-VG30, Sony NEX-VG900.
For a list of bug fixes and new lens profiles, see the Adobe Lightroom Journal.