I am just about to begin a research project for Sun on how people are using Web Services right now, and how they plan to in the near future. So we'll see how things develop... in the meantime, anything you learn about J2EE and EJB is a Really Good Thing, it seems.
And one other thing to note about Web Services, is that you might not need one. If the client that uses the Web Service is written in Java, then using a Servlet, EJB, or RMI is a better solution.
and what about AOP? aspectJ? is it becoming more popular?