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There are currently no specific plans for adding any features to specific UI components; most of the planned changes for Vaadin 7.0.0 are on a deeper framework level.
With that said, it is likely that we will review popular minor feature requests towards the end of the development cycle. This kind of feature is quite isolated and shouldn't require breaking any previous functionality, so it might as well be included for Vaadin 6.9 or Vaadin 7.1 instead of Vaadin 7.0.
We are also considering generic functionality for adding decorators (from a technical sense, not restricted to visual decoration) to components. I imagine a decorator could quite easily be used to add your desired feature, though the exact whereabouts of the decorator feature is still quite uncertain.