When ARM announced their new Cortex A17 core, I could not quite understand why they would release another core with performance and features somewhat similar to Cortex A12 and Cortex A15. Charbax interviewed Nandan Nayampally, ARM VP of Processor Marketing, at Mobile World Congress 2014 and everything is much more clear now.
Cortex A17 is based on A12, but adds support for big.LITTLE processing support with Cortex A7, and further improves performance. In some work loads Cortex A17 can currently match Cortex A15 performance, and by 2015, Cortex A17 will have performance similar to A15, and replace it in mid range devices as it has a lower footprint and lower cost. High-end products will switch to 64-Bit with Cortex A53 or A57 next year. The interviewee did not say this explicitly but it could be many companies will simply skip Cortex A12, and directly use Cortex A17, just like Rockchip decided to do with RK3288. One last interesting point is that processors using Cortex A17 are likely to use 28nm process due to cost constraints.
Actual products should start to become available in Q4 2014 / Q1 2015.