The new V10 looks very nice, and I've been a Dyson cordless fanatic since the DC16, which I bought 10 years ago. So far I've owned the DC16, the DC35 (their first stick vacuum, which I saw as revolutionary), the DC59 Animal, the V6 Absolute, and my current V8 Absolute. As I've upgraded, I've sold my previous-gen models to friends, who have all been happy with them.
Going all-cordless, although very bold, has me worried. My main concern is planned obsolescence. For instance, although my friends were happy with the DC16, it eventually simply disappeared from their house, once the battery no-longer held a charge. I'm sure my old DC35 is overdue for a new battery as well. Once the batteries wear out, like with phones and laptops, you're at the mercy of the manufacturer (or third party) to hopefully continue to produce the parts to keep it going.
My other concern is that some of Dyson's current uprights are awesome, and clean much better on carpeting than any of their cordless vacuums. Although my V8 is a fantastic and versatile machine, it doesn't deep-clean carpeting nearly as well as most of Dyson's current uprights, or most good corded vacuums in general. I can already tell their bold cleaning claims will get a smackdown in comparison tests, against most "conventional" vacuums.
I like cordless, but I like the reliability and longevity of a corded machine as well. It'll be a huge bummer if Dyson phases out corded machines completely.