IMHO, Apple will be making a Netbook at some point in time. The only reason they are stepping back is because they are scared of little profit, and the Air. That is supposed to be Apple's most mobile computer. If you think about it, nothing on the Air makes it worth it's price tag. They can only charge that much for it because it's so small and well, Apple. If Apple did release something along the spec's of a Netbook, I'd expect it to be priced anywhere between $800-$1100 USD for a BASE model of it. Would it actually be worth that much? No. Would people buy it? Yes. And most importantly, would Apple make a profit? Yes. It's just up to Apple to give it a go.
I myself have a HP Mini 1035NR. 10.2" display with a webcam built in (much like the Macbook's glossy screen), 1.6GHz Intel Atom with a Intel GMA 950 (It's actually a dual core 800Mhz), 1GB of RAM on a 533MHz FSB with a 16GB SSD from SanDisk. It is also both Bluetooth and 3G capable along with basic Wifi. And I only paid $399 for the computer itself. Now in my opinion, apple would never release a computer with such a small hard drive. So a 64GB SSD would be base. Possibly 2GB of RAM out of the box. And other then that, pretty much the same fixings as mine has but with OS X. Now, I can turn my Mini into what I just said for $620 total cost (and that's consumer cost, not bulk) less the OS X part. Apple of course would put in a better CPU and GPU and a different shell for the unit. Possibly bring the price up to the high $800 area. Add in a few hundred dollars for Apple's "Ferrari-ness" and you have yourself a Netbook that's small but usable, affordable but not cheap for an Apple, still fast compared to other Netbooks, and has that high cost high fashion look that draws so many in. Would it eat away at MacBook sales? Not one bit because it's missing a disc drive. And someone that wants an everyday laptop needs one of those without having to carry around a sack of parts. Just like how the Air isn't eating much from both the MB and MBP. (
There Apple, I just mapped out how to make a NetMac....now get to it 
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In short, I can honestly say that there will be an Apple Netbook released in the future. Who knows when Apple will finally decide to take the plunge into a bare bones "laptop". They did do it with the desktop though so....