Hi!
It is possible to invoke wsimport from both
Ant and Maven, both of which can be automated.
In Eclipse, you can configure a Builder for a project which can run a selected Ant task during a build of the project - this way it becomes integrated with the development environment.
There are probably similar features in other IDEs, but I am not familiar with the details.
As far as I know, there is no option to update existing classes. They are always overwritten.
Best wishes!