The popularity of virtualization technology and the new trend of selling instances could make operating system development interesting again.

The requirements for an operating system have changed drastically with this new way of thinking about what it means to run an operating system. The requirements can be as low as supporting a single process that can talk tcp and (maybe) to disk. Look at Haskell Network Stack, it provides network support to an application and you don't need an OS proper, just Xen.

I'm very excited to see where highly lightweight OSes end up.