I wouldn't be surprised if by the end of 2015 ARM comes with a mobile SoC more powerful than XBOX One/PS4...
I'll grant you that four A72's at their maximum clock speed might surpass the 8 Puma cores in these consoles.
But there's no way that a mobile GPU is going to surpass either console, anytime soon. Both in terms of memory bandwidth and raw compute, there's still a big gap between these GPUs and anything in the mobile space. The main issue is power consumption (and the corresponding heat dissipation). GPUs are already much more efficient than CPUs, and they're not constrained by a legacy instruction set the way x86 is. So, there's not much one can do to further improve on efficiency besides riding the process curve.
The second issue is that mobile platforms cant afford all the pins and traces you'd need for such a wide path to off-chip RAM. In 2016, we'll probably see this issue effectively eliminated by stacking HBM right in the SoC, itself. But it'll be a while longer before high-end mobile GPUs approach the shader counts or clock speeds of these guys.