The EJB 3.0 group is currently debating on whether to have this feature. I am extremely against it as JBoss has always been about NO precompilation step.
If you need to generate an interface most IDE's have a refactoring option to create an interface.
The tool is not just for precompilation step. Obviously IDEs' support is expected, but there may be occasions for developers to (have to) use a command tool on a console. In that case, annotations work just great, in other words, without any IDE's help.