The Java language has been extensively debated and argued about within Sun. Almost every language construct of existing languages has already been considered for inclusion in Java. While there may still be room for addition, it is very unlikely that your pet feature will be added to the language spec if it isn't already there. In a couple of years parameterized types (i.e. templates) may be added to the language. Otherwise the spec is pretty much frozen except for minor changes and bug fixes.
Extensions are planned for the class library though. In particular Sun is working on extensions for 3D, multimedia, telephony, and improved graphics.
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