I have reason to believe, with all the cash reserved, they are gonna take a serious step forward in low-power processors. What's this mean for us? iPhones/iPods with much more power and potential and much better battery performance.
Will this carry to the Mac? Nah, unless these chips can smoke out Intel's offering and deliver good performance per watt, Intels not going anywhere.
Apple is really obsessed with iPhone and these small products one can carry in your pocket, they are striving to put more power in your pocket then ever before.
If technology stocks really will plummet as analysts have been warning about for years, Apple will be in a prime position to make some acquisitions. Yes, their price will go down as well, but that doesn't stop them spending cash.
NVidia (NVDA)'s market cap is $4.84Bn (according to Google Finance), and they have loads of experience in chipset design and mobile and desktop graphics. Silicon Image is only worth $342Mn. Broadcom has a market cap of about $9Bn. With $25Bn, Apple could buy all of those companies in a hostile takeover (assuming regulatory approval), and have $10.7Bn in cash still sitting around. It's more complicated than that, because they'd need to integrate teams with their own product teams, but that's more a time cost than monetary cost.
With those 3 and PA Semi, Apple would be able to completely change their product profile to allow slimmer, more powerful products that are harder to compete against. NVidia and SI can make fantastic mobile GPUs with chipsets on a chip, and have the Broadcom communications chip on the same package. With a chip like that, Apple could probably shrink the iPhone's PCB by between 1/4 and 1/3, and lower power consumption considerably. If PA Semi created the ARM processor, there's no reason Apple couldn't put the whole phone on one packaged IC.
Of course, I'm just making this all up (except the market cap figures, they're real). Just to show you how much $25Bn can buy.