Unfortunately, I was not able to attend the PDC 2008.  But I have read some blog posts from some who attended yesterday.  It looks like C# 4.0 will support many dynamic typing concepts including co- and contra-variance, and although "duck typing" was not explicitly mentioned, it seems to be implied by what I read.  (Since duck typing is a principle of dynamic typing and not necessarily a feature in its own right, I am not surprised it is not named specifically.)

Now don't get me wrong, it was fun writing the duck typing library, but I would have no problem whatsoever if it were made obsolete by this.  Having the features integrated into C# would be awesome, and I'm sure it would eliminate the initial overhead caused by the dynamic compilation used by the duck typing library.

I think I will have to actually use C# 4.0 before I know how it will affect the usefulness of the duck typing library, but I am thinking right now that it may still be useful for interacting with "vintage" code libraries.  That, as I understand it, is actually what Jordan uses the library for most.  So whether C# 4.0 will fit the bill in this respect hinges on whether the dynamic typing features can be used when interacting with libraries that were not written or compiled in C# 4.0.

Unfortunately, I haven't had the chance to spend a lot of time working on the new duck typing library, which may actually have equaled wasted effort, but if such a library would still be useful with C# 4.0, I think it will change significantly from what I originally thought.  It will probably be designed specifically to complement C# 4.0 features.