Sounds like VB9 won’t have duck typing according to newson the InfoQ site. I must say that I am not surprised that this has been a difficult feature to get right in VB9, given the ability for it to exponentially grow the number of run-time errors in your application. One word that often comes up in the context of duck typing and dynamic languages for that matter is unit testing. If you are using duck typing you really need to be able to create those runtime scenarios where you application fails in a test environment. Are VB developers at the point where they are extensively unit testing their code, not sure, but it is probably safer to make sure the tooling supports duck typing as well as the language before making it available for wider consumption.
P.S. Am I getting older or wiser, when seeing the word reuse associated with duck typing that is cringe?