For that to happen, GWT needs to have ability to use more complete reflection available on the client (since the UI is created on the client at the runtime). Right now, the prototype is using great library from Robert "Kerberos" Cooper, the Gwittir, which has some support for runtime reflection, but it is far from complete. Most notably, the reflection of Annotations is missing completely.
I thought that Google GWT team is going to add those features to the core GWT one day, but it seems this is not on their to-do list at all, so we'd need to write the Annotation reflection support by ourselves.
Looking for someone who might be interested to do the same thing, we can join the forces perhaps ?
There might be a future Czech Hackathon Group session devoted to this, if we can get enough interested participants.
Here is the (ever expanding) list of pointers to documentation, tutorials and related articles :
Gwittir introspection : http://code.google.com/p/gwittir/wiki/Introspection
Generator abstraction in Rocket GWT library : http://code.google.com/p/rocket-gwt/wiki/Generator
(former) Lombardi Generator experiments blog : http://jectbd.com/?p=48