Back in 2013, Samsung announced at its Analyst Day event that it was working on a mobile application processor with ARM's 64-bit processor cores and also that it would move to a chip with its own custom cores by 2016. The former has already come to pass in the form of the Exynos 7420 that powers the Galaxy S6 and Galaxy S6 edge, and the latest report suggests Samsung will be ready with its own custom mobile CPU cores by the first quarter of next year.
For those unaware, Samsung currently licenses processor cores – called Cortex – from ARM (so do other chip makers with 64-bit SoCs, including Qualcomm for the Snapdragon 810) and then simply puts them in its Exynos chips. According to sources based in Korea, Samsung expects to “see results by Q1 next year at the latest” when it comes to the development of its custom processor cores. That's not exactly a full-on confirmation that an SoC with Samsung's custom cores will indeed make its way to devices in the beginning of 2016, but it is certainly possible we will see this chip in the Galaxy S7, given how Samsung has been getting serious about the mobile processor business.
Samsung has also been reported to be working on a custom in-house mobile GPU, though it is expected to be ready for mass production as early as mid-2015.