Adobe is rumored to be readying Photoshop CS5 for release around the end of April this year. If it seems like CS4 just came out, it was actually back in October 2008 so they are due if they keep with their recent release history. Expected features include a revolutionary new brush system that models real three dimensional paint brushes and allows for simulating paint mixing and drying over time. Photoshop CS5 is also suspected to include a new Adobe Labs technology for intelligently warping images based on content. The spot healing brush is also expected to get a makeover in order to even more seamlessly blend fixes based on image content. Selection tools are expected to get a radical makeover too allowing for much better edge detection without investing in third-party filters. Photoshop CS5 will also be the first 64-bit version released for the Macintosh. We on the Windows side have had 64-bit Photoshop since CS4. Although Adobe started out supporting Apple only, in recent years they've actually been coming out with a number of features for Windows first.
From website: Earthbound Light

