Right now the Samsung Galaxy S III has one of the best 8MP camera's of any smartphone, and has even bested the iPhone 4S camera in several reviews/articles, but that apparently isn't good enough for Samsung's next flagship. Supposedly, according to the latest rumors, the Samsung Galaxy S IV coming sometime next year will actually come with a 13MP camera. Here's a quote with some of the details,

The 13-megapixel sensor is said to have been originally intended for the third-gen Galaxy S and the second Galaxy Note, but never made it to those devices (both feature 8-megapixel shooters). If such a camera arrive in the S IV, it'd capture images with 4208 x 3120 pixel resolution.
Current rumors peg the next Samsung Galaxy S phone for a launch at Mobile World Congress in 2013, but we don't actually buy those rumors and suspect that Samsung will launch the phone with their own launch party later on in the year. Regardless, it will be interesting, although unsurprising, to see if this "new-better" camera does show up in the SGS4.

Source: S3Forums via PhonaArena