Windows 7 is specifically optimized for netbooks - it runs on 512 MiB and 16 GB disk. It runs really well on 2 GiB and 64 GB (my eeePC).
I would expect that part of the reason Snow Leopard is on a diet is for netbooks - and that probably will predict the release date of Apple's netbook.
(or 10" MacBook Air - whatever you want to call it)
Apple's Netbook will be too expensive.
When the Netbook market's flooded, then Apple will come out with a REVOLUTIONARY DEVICE, just like the iPhone...