I don't think that's true. Arm chips just don't clock as high as intels can, and no one* cares about clock speed any more. That ship has sailed. Multiprocess web browsers will drive the sales of massively multicore arms (with tons of ram!), and intel will be sunk.
It's not just about clock speed. While Intel Core CPUs don't scale down to power budgets as low as ARM cores, they are impressively efficient on a perf/watt basis. Smart phones achieve high battery life mostly by being very aggressive about reducing CPU load in software (see iOS killing apps the moment they go into the background). General purpose operating systems don't work like that so there's more reliance on the hardware to keep power draw down.
The key word there is "trying". ARM servers have had a tough time gaining traction in no small part because the hoped for power efficiency gains have not been realized.
