128 GB ram will really not make the cut, I'm guessing 32GB's, but they might opt for HBM instead of GDDR5 or DDR3 and thus remove any potential RAM bandwith bottleneck. The bottleneck might easily be the processor as it is now with the Xbox One and PS4. The PS3's Cell processor is actually more powerful than the PS4's CPU. It'll depend where AMD will be with it's big cat cores, but it'll probably be based of their yet-to-come ZEN architecture, so we might see some real CPU performance increase there. If the 9th Gen consoles want to run native 4K/60 FPS games, we're going to have to see around 12 Teraflops of raw GPU power AT LEAST to power games from 2018/2019 at that resolution and framerate.
So basically:
32GB of HBM RAM
A GPU, APU or Dual Graphics configuration with at least 12 Teraflops of GPU compute power
Newer, much more efficiënt and probably higher clocked 8-core CPU's or APU's