http://www.extremetech.com/computin...finfet-networking-chip-32-core-arm-cortex-a57
60% power reduction on 16nm @ the same speed.
Puma saves 20% at 28nm over Jaguar at 28nm. AMD will be using "Nolan" soon and considering Nintendo, they would possibly go ARM from AMD anyways. IIRC Jaguar eats 50watts, so minimum 10watts saved before the 60% here, but I'd venture to guess that ARM and newer ARM architecture would come in at a full 50% reduction before moving to 16nm.
GDDR5 would also be dropped for stacked memory, as Nintendo does spend on memory, so you'd save on power here.
GCN TDP has to evolve, recent leaked benchmarks of 390x shows a performance vs power consumption beyond Nvidia's new GPUs, so it's likely that AMD has already made some savings there that we will see shortly. I'd say even ignoring this, PS4 consumes 137 watts measured at the wall. lets place 25 watts on HDD, GDDR5 and GPU inefficiency compared to AMD's next GPU series. 25 watts on CPU efficiency improvements explained above (this is all just rough estimating for the best outcome) it's also ~85% efficiency for the PSU so lets go with 117 watts being drawn in for the system itself, -50 watts for architecture improvements from AMD, -60% for moving down to 16nm. Is it possible? ~30 watts before PSU efficiency, I'd put the actual number that above calculation gets at, but as most of those numbers are just guessed at, I don't think it's important.
Considering the specs of Nintendo's next console are pointless, I don't think this matters, the only specs we should be worried about is the handheld's, as that is the minimum and thus, baseline for graphics on Nintendo's next hardware cycle, which is why 480p-540p screens make sense, on a ~4inch device, it won't really matter much anyways.