I'd imagine eventually all "netbooks" will have multi-core processors in the future. In fact, I'd imagine once technology advances far enough where that any computer you buy is faster than you'll ever need, the netbook market will fade away. We're already there for desktop consumer use.
I get 10 hours of battery life out of my single core atom, which I am very happy with. Unfortunately it's also very slow but it serves its low-cost extended mobility purpose very well.
In 10 years if I can get i7+ performance in a machine the same size with the same battery life for the same price, why not?