That is 15w for a tablet with 10x the processing power of today's Atom.
Do you think Arm based SOC's in 2015 will have 20x the performance of today's Atom? That is what would be needed for ARM to compete at that level. -----
The 10x/20x performance improvements are impressive, but as always, the devil is in the detail. I assume (and I could be wrong), that a chunk of that performance is because the new Atom will be multi-core.
We don't know much of ARM's roadmap for 2015, but 10x would be doable with a mult-core approach while still at 1 to 2 watts.
Nvidia are claiming a x100 performance boost by 2014 (Stark) but this will be a heterogeneous chip.