That's a relatively modest increase of about 9% -- enough to be noticeable, in some tests, but unlikely to redefine the experience of using the console. The CPU clock shift probably provides a bit more power for background tasks or simultaneous processing, while rippling through the system in the form of slightly increased cache bandwidths, lower bus latencies, and a host of other small improvements. As has previously been noted, the real difference between the PS4 and Xbox one is the underlying GPU horsepower, and how much that matters won't be resolved until silicon is actually shipping for both products.
Let's take a few questions.
Could This Hurt The Console's Thermals?
Almost certainly not. Have you seen the Xbox One's fan + heatsink?
This question stems from a misunderstanding regarding the Xbox 360 and the Red Ring of Death. That problem, yes, was heat-related, but it specifically came back to the kind of lead-free solder Microsoft had used in the design. This is the kind of discussion that can quickly turn circular -- a better-designed part might not have dissipated so much heat, while a leaded solder might not have cared whether the part dissipated a lot of heat or not.
In the end, the Xbox 360's RROD issues weren't caused <em>just</em> by heat, but by the interplay between thermal expansion/contraction, the characteristics of the solder, and the Xbox's operating temperatures. The Xbox One's fan+heatsink combination is considerably more robust than the Xbox 360's, and a modest clock increase to these parts isn't going to cause any real problems.
Is This Going to Change Which Console Is Faster?
Regardless of which console you think is going to be the better deal, no, a clock speed tap to CPU and GPU isn't going to dramatically shift the balance. The fact that Microsoft is undertaking these measures at such a late date can be read as a desperate move to minimize the impact of the performance difference between the two consoles -- or as a decision made to improve task switching speed, reduce input lag, or give developers a little extra headroom when planning services and features.
Regardless of whether you think the Xbox One needs a little extra oomph, can't possibly catch up, or is already the easy choice for the next generation, an extra 5-7% real world performance between CPU and GPU combined isn't going to make a major difference. This is all about smoothing out the user experience, minimizing latency hitches, or giving developers a few extra clock cycles to plan for in the future. It's not going to be a major source of power consumption given the sophisticated power gating that the SoC supports.