I still like netbooks and feel they have their place.
My netbook (which I just recently sold..) had great battery life and had more features that I look for than those that a tablet can offer. 9 hours of battery life with the ability to do pretty much anything I could hope for (programming, typing essays, any productivity work basically). Tablets aren't really viable for that solution and I'm not sure if Ultrabooks can offer the same sort of battery life. Even if they can, their price point isn't all that appealing for myself (and I assume many others).
I do like Ultrabooks as well, though. I'm just not sure if they offer as good of battery life (which is personally my main concern). Ultrabooks do have the benefits of bigger resolutions/screens and more performance, but are those really worthwhile for everybody? My little Atom had enough kick behind it to allow me to run anything I could reasonably expect to do on the go for hours on end. The resolution would be nice but it's my fault for getting a 10" netbook in the first place.
I think continuing to offer netbooks would be a good idea for the consumer as it allows for more choice (but a terrible idea for OEMs because of a lack of profitability). They're the smallest and most affordable laptops out there that are still very capable and have their own benefits.