The big step is the desktop. The other big area to deal with is high availability clustering. I personally think the desktop or at least the thin client end of the desktop is the most important. Linux has good security features which makes it ideal for things like call centre environments, although perhaps less so for their staff. Building a thin client Linux environment with hotdesking, sensible shared file store and good network efficiency is a golden opportunity.
Total domination is bad.
The Microsoft dominance already badly misled people about how to choose systems. Instead of 'what tool do I use for the job' it's 'well it was shipped with the box'. Linux is a tool, Windows is a tool and so are numerous other systems. It's really important people go back to looking for the right tool for the job. That will never always be Linux.