Currently available (as of 2/21/14) as a release candidate, the next update for ACR and the DNG Converter has some more interesting changes than usual. First the bad news; if you are a CS6 user under Windows XP and Vista or Mac OSX 10.6 support has been dropped by Adobe. More current systems users will continue to get updated camera support through future ACR releases. New features are only available to CC users.
The primary function of updates is camera support, lens profile updates and bug fixes with an occasional modification in operation. ACR 8.4, and presumably the accompanying Lightroom update, will offer some more interesting changes. Chief among them is a new preview system with optional split view. This will simplify before and after views of image modifications. The preview checkbox is gone and replaced by a three button viewing option. They are Mode, Swap, and Copy. The single image view shows the current state of changes as always.
Side-by-side or Split-view modes will show the original image in the top or left and the updates in the bottom or right. A preview preferences dialog will allow you to set up customized views for cycling. The Q key will cycle through the view modes which can also be chosen from a menu by holding the Mode button down. The P key will swap before and after views of the selected image and adding the shift key will swap the view for all selected images. The Copy button (Alt or Option P) will copy after settings to the before image. Zooming and panning are linked for a matching view as you work. There are some other changes which you will want to explore when you get the upgrade.
A “Pet Eye” correction is available in the drop down for the Red Eye tool to fix bright pupils in animal images.
Modifications to local corrections in ACR include a global reset for correction sliders to zero. Right clicking on a Radial Filter pin will now allow you to expand the filter to the full image area.
Synchronize, New Preset, Save Settings, and Copy/Paste (Bridge) dialog boxes have added Check All and Check None shortcuts to simplify settings.
The Crop and Straighten tools have an added X key option to flip the aspect ratio from landscape to portrait or the reverse.
The Lens Correction Profile panel now indicates when automatic metadata based lens profiles are applied to the image.
The Histogram pane has an added context menu that will allow choosing L*a*b readouts even if your workflow options are set to a different color space. This menu will also allow you to toggle shadow, highlight, and gamut clipping warnings.
In all, a considerable set of changes will accompany this latest update to ACR. It will be interesting to see how these are applied to Lightroom as well.